Trinity

First published Thu Jul 23, 2009; substantive revision Thu Aug 14, 2025

A Trinity doctrine is commonly expressed as the statement that the oneGod exists as or in three equally divine “Persons”, theFather, the Son, and the Holy Spirit. Every term in this statement(God, exists, as or in, equally divine, Person) has been variouslyunderstood. The guiding principle has been the creedal declarationthat the Father, Son, and Holy Spirit of the New Testament areconsubstantial (i.e. the same in substance or essence, Greek:homoousios). Because this shared substance or essence is adivine one, this is understood to imply that all three namedindividuals are divine, and equally so. Yet the three in some sense“are” the one God of the Bible.

After its formulation and imperial enforcement towards the end of thefourth century, this sort of Christian theology reigned more or lessunchallenged. But before this, and again in post-Reformationmodernity, the origin, meaning, and justification of trinitariandoctrine has been repeatedly disputed. These debates are discussed insupplementary documents to this entry. One aspect of these debatesconcerns the logical coherence of trinitarian theology. If there arethree who are equally divine, isn’t that to say there are atleast three gods? Yet the tradition asserts exactly one god. Since therevival of analytic philosophy of religion in the 1960s, manyChristian philosophers have pursued what is now called analytictheology, in which doctrines are given formulations which are precise,and it is hoped coherent and otherwise defensible. This articlesurveys these recent versions of the Trinity doctrine developed usingthis analytic approach, leveraging concepts from contemporarymetaphysics, logic, and epistemology.

Additional material related to this entry can be found in three supplementary documents:

1. One-self Theories

One-self theories assert the Trinity, despite initial appearances, tocontain exactly one self.

1.1 Selves, gods, and modes

A self is a being who is in principle capable of knowledge,intentional action, and interpersonal relationships. A deity iscommonly understood to be a sort of extraordinary self. In the Bible,the deity Yahweh (a.k.a. “the LORD”) commands, forgives,controls history, predicts the future, occasionally appears inhumanoid form, enters into covenants with human beings, and sendsprophets, whom he even allows to argue with him. More than a commondeity in a pantheon of deities, he is portrayed as being the onecreator of the cosmos, and as having uniquely great power, knowledge,and goodness.

Trinitarians believe this revelation of the one God as a great self tohave been supplemented or superseded by later revelation showing theone God to be three “Persons” (Greek:hypostaseisorprosopa, Latin:personae). Some Trinity theoriesunderstand the Persons to be selves and then try to show that thefalsity of monotheism does not follow. (See section2 below.) A rival approach is to explain that these three divinePersons are really ways the one divine self is, that is to say, modesof the one god; this reduces all but one of the three or four apparentdivine selves (Father, Son, Spirit, the triune God) to the remainingone. That is, one of these four is the one god, and the others are hismodes. Because the New Testament seems to portray the Son and Spiritas somehow subordinate to the one God, one-self Trinity theoriesalways either reduce Father, Son, and Spirit to modes of the one,triune God, or reduce the Son and Spirit to modes of the Father, whois supposed to be numerically identical to the one God. (See section1.8 for views on which only the Holy Spirit is reduced to a mode of theFather.)

Because God in the Bible is portrayed as a great self, at the popularlevel of trinitarian Christianity one-self thinking has a firm hold.Liturgical statements, song lyrics, and sermons frequently usetrinitarian names (“Father”, “Son”,“Jesus”, “God”, etc.) as if they wereinterchangeable, co-referring terms, referring directly or indirectly(via a mode) to one and the same divine self.

1.2 What is a mode?

A mode is supposed to be a “way a thing is”, but thatmight mean several things. A “mode ofX” mightbe

an intrinsic property ofX (e.g., a power ofX,an action ofX)
a relation thatX bears to some thing or things (e.g.,X’s loving itself,X’s being greaterthanY,X appearing wonderful toY and toZ)
a state of affairs or event which includesX (e.g.,X lovingY, it being the case thatX isgreat)

One-self trinitarians often seem to have in mind the last of these.(E.g., The Son is the event of God’s relating to us as friendand savior. Or the Son is the event of God’s taking on flesh andliving and dying to reveal the Father to humankind. Or the Son is theeternal event or state of affairs of God’s living in a son-likeway.) If an event is (in the simplest case) an entity having aproperty (or a relation) at a time, then the Son (etc.) will beidentified with God’s having a certain property, or being in acertain relation, at a time (or timelessly). By a natural slide ofthought and language, the Son (or Spirit) may just be thought of andspoken of as a certain divine property, rather than God’s havingof it (e.g., God’s wisdom).

Modes may be essential to the thing or not; a mode may be something athing could exist without, or something which it must always have solong as it exists. (Or on another way to understand theessential/non-essential distinction, a mode may belong to athing’s definition or not.)

There are three ways these modes of an eternal being may be temporallyrelated to one another: maximally overlapping, non-overlapping, orpartially overlapping. First, they may be eternallyconcurrent—such that this being always, or timelessly, has allof them. Second, they may be strictly sequential (non-overlapping):first the being has only one, then only another, then only another.Finally, some of the modes may be had at the same times, partiallyoverlapping in time.

1.3 One-self Theories and “Modalism” in Theology

Influential 20th century theologians Karl Barth (1886–1968) andKarl Rahner (1904–84) endorse one-self Trinity theories andsuggest replacements for the term “Person”. They arguethat in modern times “person” has come to mean a self. Butthree divine selves would be three gods. So even if“Person” should be retained as traditional, its meaningshould be expounded using phrases like “modes of being”(Barth) or “manners of subsisting” (Rahner) (Ovey 2008,203–13; Rahner 1997, 42–45, 103–15).

Barth’s own summary of his position is:

As God is in Himself Father from all eternity, He begets Himself asthe Son from all eternity. As He is the Son from all eternity, He isbegotten of Himself as the Father from all eternity. In this eternalbegetting of Himself and being begotten of Himself, He posits Himselfa third time as the Holy Spirit, that is, as the love which unites Himin Himself. (Barth 1956, 1)

All of Barth’s capitalized pronouns here refer to one and thesame self, the self-revealing God, eternally existing in three ways.Similarly, Rahner says that God

is – at once and necessarily – the unoriginate whomediates himself to himself (Father), the one who is in truth utteredfor himself (Son), and the one who is received and accepted in lovefor himself (Spirit) – and…as a result of this,he [i.e. God] is the one who can freely communicate himself. (Rahner1997, 101–2)

Similarly, theologian Alastair McGrath writes that

when we talk about God as one person, we mean one personin themodern sense of the word [i.e. a self], and when we talk aboutGod as three persons, we mean three personsin the ancient senseof the word [i.e. a persona or role that is played]. (McGrath1988, 131)

All three theologians assume that the three modes of God are allessential and maximally overlapping.

Mainstream Christian theologians nearly always reject“modalism”, meaning a one-self theory like that ofSabellius (fl. 220), an obscure figure who was thought to teach thatthe Father, Son, and Holy Spirit are sequential, non-essential modes,something like ways God interacts with his creation. Thus, in oneepoch, God exists in the mode of Father, during the first century heexists as Son, and then after Christ’s resurrection andascension, he exists as Holy Spirit (Leftow 2004, 327; McGrath 2007,254–55). Sabellian modalism is usually rejected on the groundsthat such modes are strictly sequential, or because they are notintrinsic features of God, or because they are intrinsic but notessential features of God. The first aspect of Sabellian modalismconflicts with episodes in the New Testament where the three appearsimultaneously, such as the baptism of Jesus in Matthew 3:16–17.The last two are widely held to be objectionable because it is heldthat a doctrine of the Trinity should tell us about how God really is,not merely about how God appears, or because a trinitarian doctrineshould express (some of) God’s essence. Modern scholars callancient modalists “Modalistic Monarchians” because theyupheld the sole monarchy of the Father, or “patripassians”for their (alleged) acceptance of the view that the Father suffered inthe life of the man Jesus.

While Sabellian one-self theories were rejected for the reasons above,these reasons don’t rule out all one-self Trinity theories, suchas ones positing the Three as God’s modes in the sense of hiseternally having certain intrinsic and essential features. Sometimes aone-self Trinity doctrine is expounded as meaning this, e.g. that God(non-contingently) acts as Creator, Redeemer, and Comforter, ordescribing “God as transcendent abyss, God as particular yetunbounded intelligence, and God as the immanent creative energy ofbeing… three distinct ways of being God”, with the namedmodes being intrinsic and essential to God (Ward 2002, 236; cf. Ward2000, 90; Ward 2015).

1.4 Trinity as Incoherent

The simplest sort of one-self theory affirms that God is, becauseomniscient, omnipotent, and omnibenevolent, the one divine self, andeach Person of the Trinity just is that same self. The“Athanasian” creed (on which see section5.3) seems to imply that each Person just is God, even while beingdistinct from the other two Persons. Since the high middle ages sometrinitarians have used a Trinity Shield diagram to explain theirviews.

The traditional Trinity shield or scutum fidei (shield of faith)

If each occurrence of “is” here expresses numericalidentity, commonly expressed in modern logical notation as“=” then the chart illustrates these claims:

Father = God
Son = God
Spirit = God
Father ≠ Son
Son ≠ Spirit
Spirit ≠ Father

But the conjunction of these claims, which has been called“popular Latin trinitarianism”, is demonstrably incoherent(Layman 2016, 138–39). Because the numerical identity relationis defined as transitive and symmetrical, 1–3 imply the denialsof 4–6. If 1–6 are steps in an argument, that argument cancontinue thus:

God = Son (from 2, by the symmetry of =)
Father = Son (from 1, 7, by the transitivity of =)
God = Spirit (from 3, by the symmetry of =)
Son = Spirit (from 2, 9, by the transitivity of =)
God = Father (from 1, by the symmetry of =)
Spirit = Father (from 3, 11, the transitivity of =)

This shows that 1–3 imply the denials of 4–6, namely, 8,10, and 12. Any Trinity doctrine which implies all of 1–6 isincoherent. Less formally: it is self-evident that things which arenumerically identical to the same thing must also be numericallyidentical to one another. Thus, if each Person just is God, thatcollapses the Persons into numerically one and the same thing. But atrinitarian by definition says that the Persons are numericallydistinct from one another.

None of this is news to the Trinity theorists whose work is surveyedin this entry. Each theory here is built with a view towardsundermining the above argument. In other words, each theoristdiscussed here, with the exception of some Mysterians (see section4.2), denies that “the doctrine of the Trinity”, rightlyunderstood, implies all of 1–6. Most theories here aim forcoherence, although one (section4.3) holds that the full truth about the Trinity includes truecontradictions, although not the contradictions just mentioned.

1.5 Divine Life Streams

Brian Leftow sets the agenda for his own one-self theory in an attackon “social”, that is, multiple-self theories. (Seesections2 and3.1 below.) In contrast to these, he asserts that

there is just one divine being (or substance), God…[As ThomasAquinas says,] God begotten receives numerically the same nature Godbegetting has. To make Aquinas’ claim perfectly plain, Iintroduce a technical term, “trope”. Abel and Cain wereboth human. So they had the same nature, humanity. Yet each also hadhis own nature, and Cain’s humanity was not identical withAbel’s… A trope is an individualized case of anattribute. Their bearers individuate tropes: Cain’s humanity isdistinct from Abel’s just because it is Cain’s, notAbel’s. With this term in hand, I now restate Aquinas’claim: while Father and Son instance the divine nature (deity), theyhave but one trope of deity between them, which isGod’s…bearers individuate tropes. If the Father’sdeity is God’s, this is because the Fatherjust is God.(1999, 203–4)

Leftow characterizes this theory as “Latin”, following therecent practice of contrasting Western or Latin with Eastern or Greekor “social” Trinity theories. He considers it to be in thelineage of some prominent Latin-language theorists. (See thesupplementary document on the history of trinitarian doctrines,section 3.3.2, on Augustine, andsection 4.1, on Thomas Aquinas.) In a later discussion Leftow adds that thisTrinity theory needn’t commit to trope theory about properties.Rather, whether or not properties are tropes, “theFather’s having deity = [is numerically identical to] theSon’s having deity. For both are at bottom justGod’s having deity” (Leftow 2007, 358). Thisclaim that there is but one token of deity between the Persons isrequired by the sixth “ecumenical” council; see thesupplementary document on the history of trinitarian doctrines,section 3.4.

Leftow makes an extended analogy with time travel; just as a dancermay repeatedly time travel back to the dance stage, resulting in awhole chorus line of dancers, so God may eternally live his life inthree “streams” or “strands” (2004,312–23). Each Person-constituting “strand” ofGod’s life is supposed to count as a “complete” life(although for any one of the three, there’s more to God’slife than it) (2004, 312). Just as the many stages of thetime-traveling dancer’s life are united into stages of her bytheir being causally connected in the right way, so too, analogously,the lives of each of the three Persons count as “strandsof” the life of God because of the Father generating the Son andthe Father and the Son spirating the Spirit (313–14, cf.321–22, Leftow 2012a, 313).

Time-travel does not require that entities are four-dimensional(2012b, 337). If a single dancer, then, time travels to the past todance with herself, this does not amount to one temporal part of herdancing with a different temporal part of her. If that were so,neither dancer would be identical to the (whole, temporally extended)woman. But Leftow supposes that both would be identical with her, notmerely her temporal parts. He holds that if time travel is possible, aself may have multiple instances or iterations at a time. The Trinityis like this, subtracting out the time dimension; God, in timelesseternity, lives out three lives, or we might say exists in threeaspects. In one he’s Father, in another Son, and in another theHoly Spirit. But they are all one self, the one God as it were threetimes repeated or multiplied.

Leftow argues that his theory isn’t any undesirable form of“modalism” (i.e. aheretical one-self theory)because

Nothing in my account of the Trinity precludes saying that thePersons’ distinction is an eternal, necessary, non-successiveand intrinsic feature of God’s life, one which would be thereeven if there were no creatures. (2004, 327)

Leftow wants to show what is wrong with the following argument (2004,305–6; cf. 2007, 359):

the Father = God
the Son = God
God = God
the Father = the Son (from 1–3)
the Father generates the Son
God generates God (from 1, 2, 5).

Creedal orthodoxy requires 1–3 and 5, yet 1–3 imply theunorthodox 4, and 1, 2 and 5 imply the unorthodox (and necessarilyfalse) statement 6. So what to do? Lines 1–4 seem perfectlyclear, and the inference from 1–3 to 4 seems valid. So too doesthe inference from 1, 2, and 5 to 6. Why should 6 be thoughtimpossible? The idea is that whatever its precise meaning,“generation” is some sort of causing or originating,something in principle nothing can do to itself. One would expectLeftow, as a one-self trinitarian, to deny 1 and 2, on the groundsthat neither Father nor Son are identical to the one self which isGod, but rather, each is a mode of God. But Leftow instead argues thatpremises 1 and 2 are unclear, and that depending on how they areunderstood, the argument will either be sound but not heretical, orunsound because it is invalid, 4 not following from 1–3, and 6not following from 1, 2, and 5.

The argument seems straightforward so long as we read“Father” and “Son” as merely singularreferring terms. But Leftow asserts that they are also definitedescriptions “which may be temporally rigid or non-rigid”(Leftow 2012b, 334–35). A temporally rigid term refers to abeing at all parts of its temporal career. Thus, if “thepresident of the United States” is temporally rigid, then in theyear 2013 we may truly say that “The president of the UnitedStates lived in Indonesia”, not of course, while he waspresident, but it is true of the man who was president in 2013, thatin his past, he lived in Indonesia. If the description“president of the United States” (used in 2013) isnot temporally rigid, then it refers to Barack Obama only inthe presidential phase of his life, and so the sentence above would befalse.

“The Father”, then, is a disguised description, somethinglike “the God who is in some life unbegotten” (2012b,335). (For “the Son” we would substitute“begotten” for the last word.) Because the “=”sign can have a temporally non-rigid description on one or both sidesof it, then there can be “temporary identities”, that is,identity statements which are true only at some times but not others.Leftow gives as an example the sentence “that infant =Lincoln”; this is true when Lincoln is an infant but false whenhe has grown up. Such identity statements can only be true or falserelative to times, or to something time-like (2004, 324). If the terms“Father” and “Son” are temporally rigid, or atleast like such a term in that each applies to God at all portions ofhis life (which isn’ttemporally ordered), then 4 doesfollow from 1–3. But 4, Leftow argues, is theologicallyinnocuous, as it means something like “the God who is in somelife the Father is also the God who is in some life the Son”(2012b, 335). This is “compatible with the lives, and so thePersons, remaining distinct,” seemingly, distinct instances ofGod (each of which is identical to God), and Leftow accepts 1–4as sound only if 4 means this.

If the terms “Father” and “Son” are temporallynon–rigid, or at leastlike such a term inthat each applies to God relative to some one portion of his life butnot relative to the others, then the argument is unsound. Relative tothe Father-strand of God’s life, 1 will be true but 2 will befalse. Relative to the Son-strand, 2 will be true, but 1 will befalse. 3 and 5 will be true relative to any strand, but in any case,we will not be able to establish either 4 or 6.

Leftow’s theory depends on a concept of modes–intrinsic,essential, eternal ways God is, that is, lives or life-strands. But hedoesnot identify the “Persons” of the Trinitywith these modes. Rather, he asserts that the modes somehowconstitute, cause, or give rise to each Person (2007, 373–75).Like theories that reduce these Persons to mere modes of a self,Leftow’s theory has it that what may appear to be three selvesactually turn out to be one self, God. But they, all (apparently)three of them,just are (are numerically, absolutelyidentical to) that one self, that is, God thrice over or thricerepeated.

Some philosophers object that Leftow’s time-travel analogy isunhelpful because time-travel is impossible (Hasker 2009, 158).Similarly, one may object that Leftow is trying to illuminate theobscure (the Trinity) by the equally or more obscure (the allegedpossibility of time travel, and timeless analogues to it).

One may wonder whether Leftow’s life stream theory is reallytrinitarian. Do not his Persons really, so to speak, collapse intoone, since each is numerically identical to God? Isn’t thismodalism, rather than trinitarianism (McCall 2003, 428)? Again, onemay worry that Leftow’s concept of God being“repeated” or having multiple instances or iterations iseither incoherent or unintelligible. And how can such Persons be fullyGod or fully divine when they exist because of something which is morefundamental, God’s life-strands (Byerly 2019, 81)?

William Hasker objects that assuming Leftow’s theory,

In the Gospels, we have the spectacle of God–as–Sonpraying to himself, namely to God–as–Father… on the cross, “My God, why have you forsaken me?”On the view we are considering, this comes out as“Why haveI–as–Father forsakenmyself–as–Son?” (Hasker 2009, 166)

In reply, Leftow argues that if we accept the coherence of time travelstories, we should not be bothered by the prospect of “oneperson at one point in his life begging the same person at anotherpoint” (2012a, 321). About the cry of abandonment on the cross,Leftow urges that the New Testament reveals a Christ who (althoughdivine and so omniscient) did not have full access to his knowledge,specifically knowledge of his relation to the Father, and so Christcould not have meant what Hasker said above. Instead, he “wouldhave been using the Son’s ‘myself’ and’I,’ which … pick out only the Son” (2012a,322).

Hasker also objects that Leftow’s one–self theorycollapses the interpersonal relationships of the members of theTrinity into God’s relating to himself, and suggests that inLeftow’s view, God would enjoy self–love, but notother–love, and so would not be perfect (2009, 161–62,2012, 331). (On this sort of argument see sections2.3 and2.5 below.) Leftow replies that the self–love in question would be“relevantly like love of someone else” and so, presumably,of equal value (2012b, 339).

Does the theory imply “patripassianism”, the traditionallyrejected view that the Father suffers? (After all, the Son suffers,and both he and the Father are identical to God.) Leftow argues thatnothing heretical follows; if his analysis is right “thenclaiming that the Father is on the Cross is like claiming that TheNewborn [sic] is eligible to join the AARP [an organization forretirees]”, that is, true but misleading (2012b, 336).

1.6 Analogy to an Extended Simple

Recent metaphysicians have discussed the possibility of a simple(partless) physical object which is nonetheless spatially extended,occupying regions of space, but without having parts that occupy thesub-regions. Martin Pickup (2016) makes an analogy between this andthe idea of a triune God, inspiring his own “Latin”account. Motivated by skepticism about any three-self theory, andtaking the “Athanasian” creed as a starting point, heunderstands the claims that each Person “is God” asasserting the numerical identity of God with that Person. While God islike an extended simple, the relationships between the Persons is“analogous to the relationships between the spatial regions thatan extended simple occupies” (418).

The theological costs of this account are high; since each Person isnumerically identical with God, each Person is numerically identicalto each of the others. One accepting this account thereby denies eachof claims 4–6 in section1.4 above. In response Pickup denies that tradition requires thedistinctness of the Persons (427). Another cost is that since eachPerson is numerically the same with God and God is three Persons, eachPerson will be three Persons. Pickup concedes that such claims“sound bad” but replies that any “Latin”account of the Trinity will as such have to accept them (428).

1.7 Difficulties for One-self Theories

A one-self Trinity is hard to square with the New Testament theme ofthe interpersonal relationship between Father and Son (Layman 2016,129–30; McCall 2010, 87–88, 2014, 117–27; Plantinga1989, 23–27). Any one-self theory is also hard to square withthe Son’s role as mediator between God and humankind (Tuggy andDate 2020, 122–23). These teachings arguably assume the Son tobe a self, not a mere mode of a self, and to be a different self thanhis Father. Theories such as Ward’s (section1.3 above), which make the Son a mere mode, make him something less thana self, whereas others (see section1.6) make him a self, but the same self as his Father. Either way, the Sonseems not to be qualified either to mediate between God and humankind,or to be a friend of the one he calls “Father”.

Again, many traditional Incarnation theories assume that the eternalSon who becomes incarnate (who enters into a hypostatic union with acomplete human nature) is the same self as the historical man Jesus ofNazareth. But no mere mode could be the same self as anything, and theNew Testament seems to teach that this man was sent byanother self, God.

Some one–self theories run into trouble about God’srelation to the cosmos. If God exists necessarily and is essentiallythe creator and the redeemer of created beings in need of salvation,this implies it is not possible for there to be no creation, or forthere to be no fallen creatures; God could not have avoided creatingbeings in need of redemption. One-self trinitarians may get aroundthis by more carefully specifying the properties in question: notcreator butcreator of anything else there might be,and notredeemer butredeemer of any creatures in need ofsalvation there might be and which he should want to save.

1.8 The Holy Spirit as a Mode of God

Some ancient Christians, most 17th-19th century unitarians,present-day “biblical unitarians”, and some modernsubordinationists such as the Jehovah’s Witnesses hold the HolySpirit to be a mode of God—God’s power, presence, oraction in the world. (See the supplementary document onunitarianism.) Not implying modalism about the Son, this position is harder torefute on New Testament grounds, although mainstream theologians andsome subordinationist unitarians reject it as inconsistent with NewTestament language which arguably implies that the Holy Spirit is aself (Clarke 1738, 147). Modalists about the Spirit counter with otherbiblical language which suggests that the “Spirit of God”or “Holy Spirit” refers to either God himself, a mode ofGod (e.g., his power), or an effect of a mode of God (e.g.,supernatural human abilities such as healing). (Burnap 1845,226–52; Lardner 1793a, 79–174; Wilson 1846, 325–32.)This exegetical dispute is difficult, as all natural languages allowpersons to be described in mode-terms (“Hillary is Bill’sstrength.”) and modes to be described in language whichliterally applies only to persons. (“God’s wisdom told himnot to create beer-sap trees.”)

2. Three-self Theories

One-self Trinity theories are motivated in part by the concern that ifthere are three divine selves, this implies that there are three gods.Three-self theories, in various ways, deny this implication. They holdthe Persons of the Trinity to be selves (as defined above, section1.1). A major motivation here is that the New Testament writings seem toassume that the Father and Son (and, some also argue, the Holy Spirit)are different selves (e.g. Layman 2016, 131–32).

2.1 Relative Identity Theories

Why can’t multiple divine selves be one and the same god? Itwould seem that by being the same god, they must be numerically thesame entity; “they” are really one, and so“they” can’t differ in any way (that is, this oneentity can’t differ from itself). But then, they (really: it)can’t be different divine selves.

Relative identity theorists think there is some mistake in thisreasoning, so that things may be different somethings yet the samesomething else. They hold that the above reasoning falsely assumessomething about numerical sameness, arguing that numerical sameness,or identity, either can be or always is relative to a kind orconcept.

Relative identity theorists are concerned to rebut this sort ofargument:

The Father is God.
The Son is God.
Therefore, the Father is the Son.

If each occurrence of “is” here is interpreted as identity(“absolute” or non-relative identity), then this argumentis indisputably valid. Things identical to the same thing must also beidentical to one another. The relative identity trinitarian arguesthat one should read the “is” in 1 and 2 as meaning“is the same being as” and the “is” in 3 asmeaning “is the same divine Person as”. Doing this, onemay say that the argument is invalid, having true premises but a falseconclusion.

These theorists reject another response to the above argument, whichwould be to reject it as invalid because 1 and 2 mean that each is amode of God (see section1), and while these claims are true, they don’t imply 3, since theFather and the Son are two different modes. Against this, the theoriesof this section assume that the three Persons of the Trinity are threeselves (Rea 2009, 406. 419; van Inwagen 1995, 229–31).

Following Rea (2003) we divide relative identity trinitarian theoriesinto the pure and the impure. Pure theories accept (1) either thatthere is no such relation as absolute identity or that such statementsare definable in terms of relative-identity relations, and (2) thattrinitarian statements of sameness and difference (e.g. the Father isGod, the Father is not the Son) are to be analyzed as involvingrelative and not absolute identity relations, whereas the impuretheories accept only (2), allowing that statements about absoluteidentity (e.g. a = b) may be intelligible, true, and not definable interms of relative identity statements, against (1). (434–38)

2.1.1 Pure Relative Identity Theories

Peter Geach (1972, 1973, 1980) argues that it is meaningless to askwhether or not some a and b are “the same”; rather,sameness is relative to a sortal concept. Thus, while it is senselessto ask whether or not Paul and Saul are identical, we can ask whetheror not Paul and Saul are the same human, same person, same apostle,same animal, etc. The doctrine of the Trinity is construed as theclaim that the Father, Son, and Holy Spirit are the sameGod,but are not the samePerson. They are “God-identicalbut Person-distinct” (Rea 2003, 432).

As Joseph Jedwab explains, traditional Trinity language andcommitments arguably lead naturally to a relative identityaccount.

Prima facie, the doctrine of the Trinity implies the sortalrelativity of identity thesis, which says that where“R” and “S” are sortals, itcould be that for some x and y, x and y are the sameR butdifferentSs. The Father and the Son are the same God, elsethey are two Gods, which implies polytheism and so is false. But theFather and the Son are different divine Persons, else they are onedivine Person, which implies the Sabellian heresy and so is false. Sothe Father and the Son are the same God but different divine Persons.(2015, 124)

Geach’s approach to the Trinity is developed by Martinich (1978,1979) and Cain (1989). Jedwab (2015) criticizes Cain’s versionas implying philosophical, theological and christologicaldifficulties. Cain (2016) defends his more Geachian approach.

Pure relative identity trinitarianism depends on the controversialclaim that there’s no such relation as (non-sortal-relative,absolute) identity. Most philosophers hold, to the contrary, that theidentity relation and its logic are well-understood; such areexpounded in recent logic text-books, and philosophers frequentlyargue in ways that assume there is such a relation as identity (Baber2015, 165; Layman 2016, 141). One might turn to a weaker relativeidentity doctrine; outside the context of the Trinity, philosopherNicholas Griffin (1977; cf. Rea 2003, 435–36) has argued thatwhile thereare identity relations, they are not basic, butmust be understood in terms of relative identity relations. On eitherview, relative identity relations are fundamental.

It has been objected to Geach’s claim about the senselessness ofasking if a and b are (non-relatively) “the same”that,

Given that we have succeeded in picking out something by the use of“a” and in picking out something by the use of“b” it surely is a complete determinateproposition thata =b, that is, it is surely eithertrue or false that the item we have picked out with“a” is the item we have picked out with“b”. (Alston and Bennett 1984, 558)

Rea objects that pure relative identity theory presupposes some sortof metaphysical anti-realism, the controversial doctrine that there isno realm of real objects which exists independently of human thought(2003, 435–36). Baber replies that such worries are misguided,as the only aim of relative identity theory should be to show a way inwhich the Trinity might be coherent (2015, 170).

Trenton Merricks objects that if a and b “are the same F”,this implies that a is an F, that b is an F, and that a and b are(absolutely, non-relatively) identical. But this widely acceptedanalysis is precisely what relative identity trinitarians deny. Thisleads to the objection that relative-identity trinitarian claims areunintelligible (that is, we have no grasp of what they mean). Ifsomeone asserts that Fluffy and Spike are “the same dog”yet denies that each is a dog and that Fluffy = Spike, we have no ideawhat this person is asserting. Similarly with the claim that Fatherand Son are “the same God” but are not identical (Merricks2006, 301–5, 321; cf. Layman 2016, 141–42).

Baber (2015) replies that if the sortaldog is“dominant”, meaning that for any sortal F, if x and y arethe same dog, they will also be the same F, then the claim that Fluffyand Spike are the same dog but not absolutely identicalisintelligible. After all, we can understand that the claim implies thatFluffy and Spike are the same animal, the same pet, and so on (167).The relative identity trinitarian, Baber says, must hold that“Being does not dominate [i.e. imply sameness withrespect to]Person but rather thatPerson dominatesBeing”. However, there’s no easy way to provethis, and dominance claims are theory-relative (ibid.). Butsuch a claim will just be a part of the relative identitytheorist’s Trinity theory (169).

One may also object to either sort of relative identity account beingthe historical doctrine on the grounds that only those conversant inthe logic of the last 120 years or so have ever had a concept ofrelative identity. But this may be disputed; Anscombe and Geach (1961,118) argue that Aquinas should be interpreted along these lines,Richard Cartwright (1987, 193) claims to find the idea of relativeidentity in the works of Anselm and in the Eleventh Council of Toledo(675), and Jeffrey Brower (2004) finds a similar account in the worksof Peter Abelard. (On Aquinas, see the supplementary document on thehistory of trinitarian doctrinessection 4.) Christopher Hughes Conn (2019) argues that Anselm was the first toconsciously develop a Trinity theory involving relative identity.

2.1.2 Impure Relative Identity Theories: A Relative Identity Logic

Peter van Inwagen (1995, 2003, 2022) tries to show that there is a setof propositions representing a possibly orthodox interpretation of the“Athanasian” creed (see section5.3) which is demonstrably self-consistent, refuting claims that theTrinity doctrine is obviously self-contradictory. He formulates atrinitarian doctrine using a concept of relative identity, withoutemploying the concept of absolute identity or presupposing that thereis or isn’t such a thing (1995, 241). Specifically, he provesthat the following eight claims (understood as involving relative andnever absolute identity, the names being read as descriptions)don’t imply a contradiction in his system of relative identitylogic.

There is (exactly) one God.
There are (exactly) three divine Persons.
There are three divine Persons in one divine Being.
God is the same being as the Father.
God is a person.
God is the same person as the Father.
God is the same person as the Son.
The Son is not the same person as the Father.
God is the same being as the Father. (249, 254)

Van Inwagen neither endorses this Trinity theory, nor presumes topronounce it orthodox, and he admits that it does little to reduce themysteriousness of the traditional language.

It may be objected, as to the preceding theory, that vanInwagen’s relative identity trinitarianism is unintelligible.Merricks argues that this problem is more acute for van Inwagen thanfor Geach, as the former declines to adopt Geach’s claim thatall assertions of identity, in all domains of discourse, and ineveryday life, are sortal-relative (Merricks 2006, 302–4). Thatis, if we all understand absolute identity claims, the most naturalinterpretation of a sentence like “God is the same person as theSon” is the conjunction of these three claims: God is a person,the Son is a person, and God = the Son. If someone declined to agreewith all three of those statements yet asserted that “God is thesame person as the Son,” her meaning would be unclear.

Michael Rea (2003) objects that by remaining neutral on the issue ofidentity, van Inwagen’s theory allows that the three Persons are(absolutely) non-identical, in which case “it is hard to seewhat it could possibly mean to say that they are thesamebeing” (Rea 2003, 441). It seems that any things which arenon-identical arenot the same being. Thus, van Inwagen mustassume that there is absolute identity, and deny that this relationholds between the Persons. Thus, van Inwagen has not demonstrated theconsistency of (this version of) trinitarianism. Further, the theorydoesn’t rule out polytheism, as it doesn’t deny that thereare non-identical divine beings. In sum, the impure relative identitytrinitarian owes us a plausible and orthodox metaphysical story abouthow non-identical beings may nonetheless be “one God”, andvan Inwagen hasn’t done this, staying as he has in the realm oflogic (Rea 2003, 441–42).

In later discussions van Inwagen goes farther, claiming thattrinitarian doctrine is inconsistent “if the standard logic ofidentity is correct”, and denying there is any “relationthat is both universally reflexive [i.e., everything bears therelation to itself] and forces indiscernibility [i.e. things standingin the relation can’t differ]” (2003, 92; cf. 2022). Thus,there’s no such relation as classical or absolute identity, butthere are instead only various relative identity relations(92–93). In so doing he moves to a “pure” relativeidentity approach to the Trinity, as described in section2.1.1. Although he professes belief in the Trinity, van Inwagen does notcommit to a relative identity Trinity doctrine (2022,130–31).

Many philosophers would object that whatever reason there is tobelieve in the Trinity, it ismore obvious that there’ssuch a relation as identity, that the indiscernibility of identicalsis true, and that we do successfully use singular referring terms.

Jc Beall points out the cost of positing unmarked equivocations in thesources of trinitarian doctrine, e.g. in the “Athanasian”creed (2023a, 101, 107–8). Beall also objects that van Inwagenand other relative identity theorists have not adequately describedthe entailments of the various sorts of relative-identity claims(2023a, 102), and in particular they fail to specify sufficientconditions for the truth of claims involving them (2021,140–45). Worse, given some plausible assumptions if there arerelative identity relations then there are also absolute identityrelations, and on some other plausible assumptions contradictions comeback even while using the recommended relative identity paraphrases(2023a, 104–5, 108–11).

Vlastimil Vohánka (2013a) argues that van Inwagen has donenothing to show the logical possibility of any Trinity theory. Justbecause a set of claims can’t be proven inconsistent in vanInwagen’s relative identity logic, it doesn’t follow thatsuch claims don’t imply a contradiction, or that it ismetaphysically possible that all the claims are true. At one point vanInwagen tells a short non-theological story whose claims, whentranslated into his relative identity logic, have the same forms asthe Trinity propositions. The story, he argues, is clearly notself-contradictory; thus, he concludes, neither are the Trinitypropositions, since they have the same logical forms. In response,Vohánka concocts a short non-theological story whose claimstranslate into claims of the same form in relative identity logic yetare clearly logically impossible (207–11). He concludesthat “there’s no ground for thinking that formalconsistency in [relative identity logic] guarantees logicalpossibility”, and that “sharing a form in [relativeidentity logic] with a logically possible proposition does notguarantee logical possibility” (211–12). Van Inwagenagrees (2022, 124–25).

2.1.3 Impure Relative Identity Theories: Constitution Trinitarianism

Another theory claims to possess the sort of metaphysical story vanInwagen’s theory lacks. Based on the metaphysical concept ofconstitution, Rea and Brower develop a three-self Trinity theoryaccording to which each Person is non-identical to the others, as wellas to God, but is nonetheless “numerically the same” asall of them (Brower and Rea 2005a; Rea 2009, 2011). They employ ananalogy between the Christian God and material objects. When we lookat a bronze statue of Athena, we’re viewing one material object,yet we can distinguish the lump of bronze from the statue. Thesecannot be identical, as they differ (e.g., the lump could, but thestatue couldn’t survive being smashed flat). We should say thatthe lump and statue stand in a relation of “accidentalsameness”. This means that they needn’t be, but in factare “numerically the same” without being identical. Whilethey are numerically one physical object, they are two hylomorphiccompounds, that is, two compounds of form and matter, sharing theirmatter. This, they hold, is a plausible solution to the problem ofmaterial constitution (Rea 1995).

Similarly, the Persons of the Trinity are so many selves constitutedby the same stuff (or something analogous to a stuff). These selves,like the lump and statue, are numerically the same without beingidentical, but they don’t stand in a relation ofaccidental sameness, as they could not fail to be related inthis way. Father, Son, and Spirit are three quasi form-mattercompounds. The forms are properties like “being the Father,being the Son, and being the Spirit; or perhaps being Unbegotten,being Begotten and Proceeding” (Rea 2009, 419). The singlesubject of those properties is “something that plays the role ofmatter,” which Rea calls “the divine essence” or“the divine nature” (Brower and Rea 2005a, 68; Rea 2009,420). Whereas in the earlier discussion “the divine essence [is]not… an individual thing in its own right” (Brower andRea 2005a, 68; cf. Craig 2005, 79), in a later piece, Rea holds thedivine nature to be a substance (i.e. an entity, an individual being),and moreover “numerically the same” substance as each ofthe three. Thus, it isn’t a fourth substance; nor is it a fourthdivine Person, as it isn’t, like each of the three, aform-(quasi-)matter compound, but only something analogous to a lumpof matter, something which constitutes each of the Three (Rea 2009,420; Rea 2011, sec. 6). Rea adds that this divine nature is afundamental power which is sharable and multiply locatable. Hedoesn’t say whether it is either universal or particular,saying, “I am unsure whether I buy into the universal/particulardistinction” (Rea 2011, sec. 6). All properties, in his view,are powers, and vice versa. Thus, this divine nature is both a powerand a property, and it plays a role like that of matter in theTrinity.

This three-self theory may be illustrated as follows (Tuggy 2013,134).

A representation of Constitution Trinitarianism

There would seem to be seven realities here, none of which is(absolutely) identical to any of the others. Four of them areproperties: the divine nature (d), being unbegotten (u), beingbegotten (b), and proceeding (p). Three are hylomorphic (form-matter)compounds: Father, Son, and Holy Spirit (f, s, h)–each with theproperty d playing the role of matter within it, and each having itsown additional property (respectively: u, b, and p) playing the roleof form within it. Each of these compounds is a divine self. The ovalscan be taken to represent the three hylomorphs (form-matter compounds)or the three hylomorphic compounding relations which obtain among theseven realities posited. Three of these seven (f, s, h) are to becounted as one god, because they are hylomorphs with only one divinenature (d) between them. Thus, of the seven items, three areproperties (u, b, p), three are substances which are hylomorphiccompounds (f, s, h), and one is both a property and a substance, but asimple substance, not a compound one (d).

Brower and Rea argue that their theory stands a better chance of beingorthodox than its competitors, and urge in its favor that leadingmedieval trinitarians such as Augustine, Anselm, and Aquinas saythings which seem to require a concept of numerical sameness withoutidentity. (See Marenbon 2007, Brower 2004, and the supplementarydocument on the history of Trinity theories, sections3.3.2, on Augustine, and4.1, on Thomas Aquinas.)

In contrast to other relative-identity theories, this theory seemswell-motivated, for its authors can point to something outsidetrinitarian theology which requires the controversial concept ofnumerical sameness without identity. This concept, they can argue, wasnot concocted solely to acquit the trinitarian of inconsistency. Butthis strength is also its weakness, for philosophers are heavilydivided on the reality, nature, and metaphysical utility ofconstitution. Some deny that a metaphysics of material objects shouldinvolve constitution, since strictly speaking there are no statues orpillars, for these apparent objects should be understood as mere modesof the particles that compose them. Arguably, truths about statues andpillars supervene on truths about arrangements of particles (Byerly2019, 82–83).

This Constitution theory has been criticized as underdeveloped,unclear in its aims, unintelligible, incompatible with self-evidenttruths, unorthodox relative to Roman Catholicism, polytheistic and notmonotheistic, not truly trinitarian, involving too many divineindividuals (primary substances), out of step with the broadhistorical catholic tradition, implying that the Persons of theTrinity can’t simultaneously differ in non-modal andnon-temporal properties, not a theological improvement over simplerrelative identity approaches, and as wrongly implying that terms like“God” are systematically ambiguous (Craig 2005; Hasker2010b; Hughes 2009; Layman 2016; Leftow 2018; Pruss 2009; Tuggy2013).

2.1.4 Impure Relative Identity Theories: Conciliar Social Theory

Scott Williams has constructed a similar theory in a series ofarticles and a book (Williams 2013, 2017, 2020, 2021, 2022a, 2024);this was formerly dubbed a “Latin Social Trinity”, but nowthe preferred term is “Conciliar Social Trinity”. One ofseveral motivations for this theory is to build a theory consistentwith the requirements of all seven “ecumenical” councils(Williams 2022, sec. 3; 2024, 3; see also section5.3 below).

In common with Leftow’s “Latin” theory andHasker’s “Social” theory (see sections1.5,2.4), Williams says that there is one “concreteinstance or trope of the divine nature” which is a constituentof each Person. Each Person is also constituted by an incommunicableattribute, begetting (Father), being begotten (Son), and beingspirated (Spirit) (2017, 324). He understands each Person to be“an incommunicable existence of an intellectual nature”(326). In his view any person is a person “ontologically andexplanatorily prior to any cognitive acts of volitions that thatperson in question has or might have” (2017, 327; cf. 2013,2019). Each Person is essentially numerically the same essence as theone divine essence, while being a numerically different Person fromthe other two Persons. Thus, the account involves irreduciblerelations of kind-relative numerical sameness. In a later pieceWilliams clarifies that to say that “The Father is God” isto be understood as “numerical predication”; the meaningis that the divine nature is a constituent of the Father. But unlikealleged cases of “numerical sameness without identity”,this relation between the divine nature and the Father is asymmetrical(2024, 27–29). But the divine Persons are not (absolutely)numerically identical to one another, and each is not (absolutely)numerically identical to the divine essence. This divine essence islike an Aristotelian first substance in that it exists on its own (notin another) and in being a concrete particular, but unlike firstsubstances it is communicable, in other words, it can be shared bynon-identical things, the divine Persons (2017, 326). The term“God” can refer to any of the Persons, or to the divineessence. The term “Trinity” is a plural-referring termwhich refers to the plurality of the divine Persons (2013, 85). (Seesection5.1.)

Williams considers it an axiom of trinitarian theorizing that“the divine persons are necessarily unified or necessarily agreeregarding all things” (2017, 321). Some rival theories try toaccount for this “necessary agreement thesis” by showinghow, allegedly, the Persons would have to come up with some policywhich would prevent disagreement. Williams finds such claims“philosophically unsatisfying”, and instead argues thatthe three Persons can never disagree because they have numerically onewill, one power of choosing (322). Unlike any other three persons, thePersons of the Trinity, because they share one divine nature, shareone set of powers, and so any exercise of any divine power belongs toeach of the three. In this case, Williams analyzes thinking asproducing and using a token sentence in what we might call divinementalese. Building on work by John Perry on indexical terms like“I”, Williams points out that a single token of a sentencein English may be used by different agents, and may thus have multiplemeanings. For example,

Suppose that Peter produces…a sign that reads, “I amhappy,” and that Peter uses this sign by holding it up. Peteraffirms that Peter is happy. Later, Peter puts the sign on the groundand Paul picks up the same sign and holds it up such that Paul affirmsthat Paul is happy. Paul uses numerically the same token as Peter did,yet when Paul uses it he affirms something different than Peter.(2013, 81)

Similarly, if divine Persons think using a language-like divinementalese, then one token of this may be used by different Persons andhave a different significance for each. The idea is that a personrelates to a proposition (the content of his thought) by means of atoken sentence which he produces and uses to think. But these mentalacts, given that the Persons share one set of powers, must be sharedby all three of them. Yet, the thoughts thereby thought will differ.For example,

if the Father uses a mental token of “I am God the Father”and in so doing affirms a proposition, then the Father affirms thatGod the Father is identical to God the Father. If the Son uses thesame mental token of “I am God the Father”… the Sonaffirms the proposition that the Son is essentially numerically thesame divine nature as the Father without being identical to theFather. (2017, 331)

This account denies as an ungrounded modern assumption that“distinct and incommunicable intellectual acts and volitionalacts are necessary conditions for being a person” (339). Whileit employs recent thinking about indexical terms and other matters,Williams considers this account to fit well with historicaltheologians such as Gregory of Nyssa, Henry of Ghent, and John DunsScotus (345). That the persons share all mental acts does not implythat they share one mind or that there is one consciousness in theTrinity. Rather, the access consciousness, experiential consciousness,and introspective consciousness of each Person may differ (2020,102–7).

A New Testament reader might question the assumption that the Personsof the Trinity can’t differ with respect to will, given thetemptation of the Son (but not of the Father) and an occasion when theSon asked the Father to be excused from a difficult trial (Matthew4:1–11; James 1:13; Mark 14:36).

In a response, William Hasker objects that it seems that sometimeshuman beings can think without using any language. Why, then, shouldwe suppose divine Persons to think only by means of mental tokensentences? Perhaps they can just relate directly to propositions (thecontents of their thoughts). Worse, Williams posits that this divinemental language is ambiguous, but Hasker says, “we wouldnaturally expect a divine language of thought to be very preciseindeed, perhaps maximally so” (Hasker 2018b, 364). He alsoobjects that the theory wrongly counts mental acts and has variousproblems of coherence and intelligibility.

Williams replies that divine mental tokens are needed “toexplain why a divine person’s mental act is directed at (amongall possible propositions) the proposition it is directed at”(2020, 115). He denies that ambiguity is always an imperfection of alanguage and urges that there is nothing objectionable about divinePersons using mental tokens that can be used to express variouspropositions (110–11). This complex dialectic unfolds in aseries of articles in the journalFaith and Philosophy; thedetails are beyond the scope of this entry.

2.1.5 Impure Relative Identity Theories: Episodic Personhood

Another relative identity theory by Justin Mooney (2021) depends on anentirely different metaphysical account to show how multiple personsmay each be the same being. Metaphysician Ned Markosian proposes athought experiment in which a man dies and is mummified, and then along time later the mummy’s parts are re-arranged into a livingwoman who has an utterly different psychology than the dead man. Thepoint is that the woman is the same object as the man but is not thesame person as the man, because the instances of personhood in hislife aren’t part of the same episode of personhood(656–56). Mooney applies Markosian’s ideas about“identity under a sortal” to the Trinity. On this account,“God is a single, divine substance that is simultaneously oratemporally participating in three distinct episodes ofpersonhood–those of the Father, Son, and Spirit” (658).Thus, each Person just is God, but none is the same Person as anyother divine Person. The account may be illustrated by modifying thetraditional Trinity shield:

An illustration of Mooney's relative identity theory of the Trinity.

On this theory, being different Persons doesn’t imply beingnumerically distinct.

One may worry that such Persons must be one and the same Person sincethey have but one substance between them, but Mooney answers that theyare individuated by their causal relationships, following Swinburne(1994). In addition, following Effingham, he says that they are notone and the same Person because they aren’t linked by immanentcausal relations. (658–59) These are “those causal linksan entity bears to itself from one time to another whereby the way itis earlier on causes how it is later on” (Effingham 2015, 35).Following Moreland and Craig (2017), Mooney adds that God possessesthree mental faculties, each had by one of the Persons (659). Finally,adapting ideas from Swinburne (1994), he says that

the Father’s episode of personhood occurs simply because God isa divine being, and a divine being is essentially a personal being. Bynature, God instantiates whatever psychological properties arenecessary for being a person. The Son’s episode of personhoodoccurs because the Father wills that there is an instantiation ofpersonhood by the divine substance which is not immanent-causallylinked to the Father’s instantiation of personhood. And theSpirit’s episode occurs because one or both of these personswill(s) that there is yet another instantiation of personhood by thedivine substance which is not connected by immanent causal relationsto either the Father’s or the Son’s instantiation ofpersonhood. (659)

He remains neutral on whether this process is either temporal ornecessary.

Unlike other relative identity theories, this account, like someone-self theories, affirms the absolute identity of each Person withGod; each is the same thing or being or primary substance, God. Thisgenerates a concern that the account may be heretical modalism. Mooneyreplies that “if Markosian’s episodic view of personalidentity is right, the model is not modalist” (660). The reasonis that on this account there are three episodes of personhood, whichimplies that there are three Persons, even though there is one beingwhich is the component thing in each episode, a single subject of theproperties that are involved in being a Person.

Even though the account has it that these three are different Persons,still, it identifies each with God, which entails their identity withone another; being the same thing as God, they must be the same thingas each other. Given this, it would seem that they can’t differin any way, e.g. the Son becomes incarnate but the Father does not(660). Mooney replies that the Trinity is mysterious, and thatprobably a sentence like “The Son became incarnate but theFather didn’t” might be understood as not requiring asimultaneous or eternal difference between the being that is the Sonand the one which is the Father. In Markosian’s thoughtexperiment, one would think that person-names would track with thedifferent stages in the career of the one object, so that, say,“Alice” would refer to the thing only in its lateststages, and “Bob” would apply to it only in its pre-mummycareer. Thus, names like “Father” and “Son”should refer to God only in one or the other of God’sPerson-episodes. Mooney suggests, then, that “The Son becameincarnate but the Father didn’t” will be true if and onlyif the Son but not the Father is the same person as someone who becameincarnate, that is, God becomes incarnate in the Person-episodeassociated with the name “Son” but not in the oneassociated with “Father” (661).

This, Mooney argues, shows why when counting objects, we should countby (absolute) identity, while when counting persons we should count bythe relation same-person. In the Trinity, then, we count one thing butthree Persons; the Persons are the same thing but different Persons(662). The account also solves his “problem of Triunity”(2018), which is that as normally analyzed, these three statementscan’t all be true, and yet arguably a trinitarian is committedto all three of them:

God is triune.
The Son is God.
The Son is not triune. (2021, 663)

The solution is that even though “strictly speaking, the Son istriune” since the Son just is God and God is triune, the meaningof 3 is that “the Son is not thesame person as anyonewho is triune”, which is both true and consistent with 1 and 2.Mooney adds that the property being triune should not be confused withthe property of being the same Person as someone who is triune; onlythe first, in his view, is an essential divine attribute(663–64).

Mooney argues that this account also solves problems relating todivine processions and aseity. The Son, being God, must have theproperty of aseity. But Mooney suggests that the Father’sgeneration of the Son doesn’t explain the Son’s existence(which would rule out the Son’s aseity), but only theSon’s being a person distinct from the Father (665).

The viability of this theory rests on a particular metaphysics ofpersonhood. One might think, contra Markosian and Mooney, that thewoman in the story is one being, the mummy is a second being (eventhough composed of many or all of the same parts), and the man is athird being. Similarly, one may wonder whether numerically distinctPersons can each be numerically the same as one god. The theoryimplies the falsity of the principle that for any x and y, if they aredifferent Fs, then x is an F, y is an F, and x ≠ y. One might alsoquestion the theory’s way of dealing with apparent differencesbetween the (numerically identical) Persons; any differences of theform “the Father is F but the Son is not F” are analyzedas meaning “the Father is the same Person as someone who is Fand the Son is not the same Person as someone who is F”. Doesthe original claim really mean what the analysis says?

2.2 20th Century Theologians and “Social” Theories

Some influential 20th-century theologians interpreted the Trinity ascontaining just one self. (See section1.3 above.) In the second half of the century, many theologians reactedagainst one-self theories, criticizing them as modalist or as somehownear-modalist. This period also saw the wide and often uncriticaladoption of a paradigm for classifying Trinity theories which derivesfrom 19th c. French Catholic theologian Théodore deRégnon (Barnes 1995). On this paradigm, Western or Latin orAugustinian theories are contrasted with Eastern or Greek orCappadocian theories, and the difference between the camps is said tobe merely one of emphases or “starting points”. TheWestern theories, it is said, emphasize or “start with”God’s oneness, and try to show how God is also three, whereasthe Eastern theories emphasize or “start with” God’sthreeness, and try to show how God is also one. The two are thought toemphasize, respectively, psychological or social analogies forunderstanding the Trinity, and so the latter is often called“social” trinitarianism. But this paradigm is now widelyrejected as unhelpful and simply not accurate to the history ofTrinitarian theology (Cross 2002, 2009; Holmes 2012; McCall 2003;Williams 2022b, 356–57).

Although the language of “Latin” vs. “social”Trinity theories has been adopted by many analytic philosophers (e.g.Leftow 1999; Hasker 2010c), these have interpreted the differenttheories as logically inconsistent (i.e. such that both can’t betrue), and not merely as differing in style, emphasis, orsequence.

Some 20th century theological sources, accepting the de Régnonparadigm, blame the Western tradition for “overemphasizing theoneness” of God, and recommend that balance may be restored bylooking to the Eastern tradition. A number of concerns characterizetheologians in this 20th and 21st century movement of“social” trinitarianism:

Preserving genuinely interpersonal relationships between thePersons of the Trinity, particularly the Father and the Son.
Doing justice to the New Testament idea of Christ as a personalmediator between God and humankind.
Suspicion that the “static” categories of Greekphilosophy have in previous trinitarian theologies obscured thedynamic and personal nature of the triune God.
Concern that traditional or Western trinitarian theology has madethe doctrine irrelevant to practical concerns such as politics, genderrelations, and family life.
The idea that to be Love itself, or for God to be perfectlyloving, God must contain three subjects or persons (or at any rate,more than one). (See sections2.3 and2.5.)

(For surveys of this literature see Kärkkäinen 2007; Olsonand Hall 2002, 95–115; Peters 1993, 103–45.) These writersare often unclear about what Trinity theory they’re endorsing.The views seem to range from tritheism, to the idea that the Trinityis an event, to something that differs only slightly, or only inemphasis, from pro-Nicene or one-self theories (see section1 and section3.3 of the supplementary document on the history of trinitariandoctrines). Merricks observes that some views advertised as“social trinitarianism” make it “sound equivalent tothe thesis that the Doctrine of the Trinity is true but modalism isfalse” (Merricks 2006, 306). However, a number of Christianphilosophers, and some theologians employing the methods of analyticphilosophy, have started with this literature and then proceeded todevelop relatively clear three-self Trinity theories, which aresurveyed here. They differ in how they attempt to secure monotheism(Leftow 1999). There are many such Trinity theories, and it is notclear that all the options have yet been explored (Davidson 2016).

2.3 Ersatz Monotheism

A problem for any three-self Trinity theory is that numerically threeselves seem to be numerically three things. And according to a theoryof essences or natures, a thing which has or which is an instance ofan essence or nature is thereby a thing of a certain kind. All Trinitytheories include the Nicene claim that the Persons of the Trinity havebetween them but one essence or nature, the divine one. But it wouldseem that by definition a thing with the divine essence is a god, andso three such things would be three gods.

Some three-self theories in effect concede that they imply tritheism(three things, each of which has properties sufficient for being agod), but argue that surely a correct Trinity theory can’t avoidthe right type of tritheism, and can avoid any undesirable tritheism,such as ones involving unequal divinity of the Persons, Persons whichare in some sense independent, or Persons who are in principleseparable (McCall 2010, 2014; Plantinga 1988, 1989; Yandell 2010,2015).

Richard Swinburne has developed a type of three-self Trinity theorywhich in the eyes of most critics seems to be “a fairlystraightforward form of tritheism” (Alston 1997, 55; see alsoBeall 2023a, 100; Clark 1996; Davidson 2016; Feser 1997; Howard-Snyder2015a; Rea 2006; van Inwagen and Howard-Snyder 1998; van Inwagen 2003,88; Vohánka 2014, 56). In a series of articles and booksSwinburne’s views have changed in significant ways (Swinburne1988, 1994, 2008, 2018), but this entry focuses on his latest work onthe Trinity.

Swinburne aims to build his theory on widespread traditionalagreements between most catholic theologians since at least the fourthand fifth centuries (Swinburne 2018, 419). The Persons of the Trinityare three beings, each a self which satisfies Boethius’sdefinition of a “person” as “an individual substance(substantia) of a rational nature” (421). Each isdivine in that each has all the divine attributes. “A divineperson is naturally understood as one who is essentially eternallyomnipotent and exists (in some sense) ‘necessarily’” (427). He argues that omnipotence entails perfect goodness andomniscience. While all three of the Persons exist necessarily(inevitably), the Father does this independently while the Son andSpirit exist of necessity dependently, because necessarily, the Fatherexists, and his existence implies that he causes them (437, n. 14).These actions of the Father are inevitable and not voluntary, but theyare via the Father’s will (425, 428). This causing istraditionally described as the eternal generation of the Son by theFather, and the eternal proceeding of the Spirit from the Father, orfrom the Father and the Son. For Swinburne, the Son is “causedby the Father alone” while the Spirit is “caused by theFather and/or through the Son” (429). The theory then iscommitted to one of these two models of the divine processions.

Father causing the Son and the two of the causing the Spirit, or the Father causing the Son and the Father causing the Spirit through the Son

Swinburne has constructed a couple versions of an argument whichpurports to show why, if there is at least one divine being or Person,there must be exactly three, with the second and third causedultimately by the first. In other words, given that it is possiblethat there be a divine Person, it is metaphysically impossible thatthere be only one, and it is metaphysically necessary that there beexactly three. Most trinitarians have assumed that such an argument isneither possible nor desirable, as the Trinity can be known only bydivine revelation. Against this, Swinburne says that “even ifyou regard the New Testament as an infallible source of doctrine, youcannot derive from it a doctrine of the Trinity”, because whenit comes to passages about the Spirit,

there are non-Trinitarian ways of interpreting…[these] whichare just as plausible as interpreting them as expressing the doctrinethat the Holy Spirit is a divine person…So unless Christianstoday recognize some good a priori argument for a doctrine of theTrinity (and most of them do not recognize such an argument), orunless they consider that the fact that the subsequent Church taught adoctrine of the Trinity is a significant reason for interpreting therelevant passages in a Trinitarian way, it seems to me that mostChristians today (that is, those not acquainted with any a prioriargument for its truth) would not be justified in believing thedoctrine. (419–20)

One may wonder if there could be two omnipotent beings; there havebeen arguments from theism (at least one god) to monotheism (exactlyone god) based on the idea that it’d be impossible for there tobe more than one who is omnipotent. (See the Monotheism entry, section5.) Suppose that one omnipotent being willed a certain object to move andsimultaneously another omnipotent being willed that it should remainin place. It would seem that whether the object moves or stays inplace, one of the being’s wills is thwarted, so that, contraryto our stipulation, one of them fails to be omnipotent. Swinburneargues that such conflicts of will are impossible given theomniscience, perfect goodness, and causal relations of the omnipotentbeings. In his view, in causing the Son and Spirit, the Father must“lay down the rules determining who has the right to do whichactions; and the other members of the Trinity would recognize hisright, as the source of their being to lay them down” (428).

Inspired by similar arguments given by Richard of St.-Victor (d.1173), Swinburne argues that a divine Person must be perfect in love.But

perfect love must be fully mutual love, reciprocated in kind andquantity, involving total sharing, the kind of love involved in aperfect marriage; and only a being who could share with him the ruleof the universe could fully reciprocate the love of anothersuch…it would be a unique best action for the Father to causethe existence of the Son, and so inevitably he would do so…ateach moment of everlasting time the Father must always cause the Sonto exist, and so always keep the Son in being. (429–30)

Thus, if there is one divine Person, there must also be another.Further, there must be a third, for

A twosome can be selfish…Perfect love for a beloved…mustinvolve the wish that the beloved should be loved by someone elsealso. Hence it will be a unique best action for the Father to causethe existence of a third divine being whom Father and Son could loveand by whom each could be loved. Hence the Holy Spirit. And I suggestthat it would be best if the Father included the Son as co-cause (ashe is of all other actions of the Father) in causing the Spirit. Andagain they must have caused the Spirit to exist at each past moment ofeverlasting time. Hence the Trinity must always have existed. (430)

What stops this process of deity-proliferation from careening intofour, seventy-four, or four million divine Persons? Swinburne repliesthat it isnot better to cause four (or more) divine Personsthan it is to cause three, since

when there is an infinite series of incompatible possible goodactions, each better than the previous one, available to some agent,it is not logically possible that he do the best one–becausethere is no best action. An agent is perfectly good in that situationif he does any one of those good actions. So since to bring about onlythree divine persons would be incompatible with an alternative actionof bringing about only four divine persons, and so generally, theperfect goodness of the Father would be satisfied by his bringingabout only two further divine persons. He does not have to bring abouta fourth divine person in order to fulfil his divine nature. To createa fourth divine person would therefore be an act of will, not an actof nature. But then any fourth divine person would not existnecessarily in the sense in which the second and third divine personsexist necessarily–his existence would not be a necessaryconsequence of the existence of a necessary being; and hence he wouldnot be divine. So there cannot be a fourth divine person. There mustbe and can only be three divine persons. (430–31)

In sum, divinity implies “perfect love” which impliesexactly three divine Persons.

Lebens and Tuggy (2019) object that such arguments trade on theambiguity of “perfect love”. Divinity, by implying moralperfection, implies the character trait of being perfectly loving. Butsomeone may have this and yet not be in the sort of interpersonalrelationship that Swinburne describes as “perfect love”.(See also Tuggy 2021.) Using familial analogies, Brian Leftowchallenges Swinburne’s claim that the three would lack anoverriding reason to produce a fourth, noting that “Cooperatingwith two to love yet another is a greater ‘balancing act’than cooperating with one to love yet another” (1999, 241).

Tuggy (2004) objects that if a three-self theory likeSwinburne’s were true, it would seem that one or more members ofthe Trinity have wrongfully deceived us by leading us to falselybelieve that there is only one divine self. He also argues that theNew Testament writings assume that “God” and “theFather of Jesus” (in all but a few cases) co-refer, reflectingthe assumption that God and the Father are numerically the same. (Seealso Tuggy 2019.) Denying this last claim, he argues, amounts toan uncharitable and unreasonable attribution of a serious confusion tothe New Testament writers and (if they’re to be believed) toJesus as well. These arguments are rebutted by William Hasker (2009)and the argument is continued in Hasker 2011 and Tuggy 2014.

The most common objection to Swinburne’s Trinity theory is thatit is tritheism and not monotheism. Looking, for instance, at thisaccount of divine processions, a reader wonders why this doesn’tamount to one god eternally causing a second god, and with that secondgod eternally causing a third god. To assuage such concerns, Swinburneargues that on his model of the Trinity, it is natural to say thatthere is “one God”. Swinburne observes that the Greektheos (and equally the Latindeus) may be usedeither as a name, a singular referring term picking out a certainindividual thing, or as a predicate, a descriptive word equivalent inmeaning to “divine”, which might in principle be appliedto more than one thing. Then he observes,

While no doubt the Fathers of the [381] Council did not have a clearview of what was the sense in which there is just one“God” and the sense in which each of the three beings is“God” the distinction between the two senses of thecrucial words makes available one obvious way of resolving theapparent contradiction. This is by thinking of these words as havingthe former sense [i.e. referring to one thing like a name] when theCreed says that there is “one God”, and as having thelatter sense [i.e. being equivalent to the adjective“divine”] when it claims that each of the beings “isGod.” Thus understood, the Creed is saying that there is oneunique thing which it names “God,” which consists of threebeings. (420)

The suggestion is that the tradition is somewhat confused, and weshould charitably interpret its talk of “one God” asreferring to the Trinity. (However, see the opening line of the Nicenecreed.) What sort of thing is this Trinity? It is not a divine Personand is not a thing (Person or not) with the divine essence. Rather, itis a thing of which the three divine beings (selves, persons) areproper parts (425). Despite this complex entity not having the divineessence (and so, not being a god), Swinburne sometimes refers to it as“God himself” (424). He argues that these three beingscan’t help but cooperate, and so agrees with the traditionalclaim that apart from the aforementioned eternal causings of oneanother, any act of one Person of the Trinity is an act of all threePersons (425). In sum, “This common omnipotence, omniscience,and perfect goodness in the community of action makes it that casethat in a natural sense there is one God” (428). That is, giventhe three divine beings described above, it is “natural”,when it comes to the name-like use of the word “God,” toapply the term to that thing which is the whole consisting of thosethree Persons. But it remains that there are three things here each ofwhich is divine, and that this whole is not itself divine; it’shard to see why this is monotheism and not tritheism.

Brian Leftow objects that in Swinburne’s account God is notitself divine. Nor does it makes sense to worship it, as it is not thesort of thing which can be aware of our addressing it. Further, theissue of monotheism isn’t the issue of how unified the divinebeings are, but rather of how many there are.

it is hardly plausible that Greek paganism would have been a form ofmonotheism had Zeus & Co. been more alike, better behaved, andlinked by the right causal connections. (Leftow 1999, 232; cf. Rea2006)

Moreover, Swinburne’s theory entails serious inequalities ofpower among the Three, jeopardizes the personhood of each, and carriesthe serious price of allowing (contrary to most theists) that a divinebeing may be created, and the possibility of more than one divinebeing (Leftow 1999, 236–40).

Daniel Howard-Snyder (2016) argues that Swinburne is committed todescriptive polytheism, normative polytheism, and cultic polytheism,and so is a “polytheistpar excellence”. He alsoargues that Swinburne’s account of the Trinity isunorthodox.

Daniel Spencer (2019) argues that the several factors which Swinburneand others appeal to in order to lend some sort of unity to the threepersons are inadequate to show how they amount to one God and notthree gods. At best we get three divine beings who in some waysresemble a god. Spencer observes that sometimes Swinburne simplyaccepts tritheism, as when he says that there are three divineindividuals or beings (Spencer 2019, 192, 198 n. 2; Swinburne 1994,170, 179). In his first treatment of the subject Swinburne talks of“three Gods” (Swinburne 1988, 234). In later writings hedoesn’t use that phrase, but his conception of the Persons issubstantially the same. Spencer observes that in principle, making thePersons proper parts of a whole which is the only God might do thetrick (195–96), and Swinburne does suggest that there is apart-whole relationship between the Persons and God; however, forSwinburne the whole is not a god.

Perhaps the most sympathetic voice in the literature is William Hasker(2013, ch. 18), but in the end he agrees that Swinburne has not doneenough to unify the Persons. (Hasker 2013b, chs. 25–28, 2018,5–7; Swinburne 2014)

2.4 Trope-Constitution Monotheism

William Hasker (2013b, 2024) has constructed what is arguably the mostdeveloped three-self theory of the Trinity. As with Swinburne, histhoughts have developed over decades, but this entry will focus on hisrecent publications. For Hasker, following Plantinga, the Persons ofthe Trinity are “distinct centers of knowledge, will, love, andaction…persons in some full sense of the term”(2013b, 22, cf. ch. 24). Hasker argues that such a view is widespreadin ancient sources, including Gregory of Nyssa and Augustine (chs.4–5, 9). While we can’t reasonably retain the ancientdoctrine of divine simplicity (ch. 7, 2016, 2018a, 7–8,18–19), we ought to uphold as many of the traditional claims aspossible, for we should assume divine guidance of theologicaldevelopment, even though “the Church’s doctrine of theTrinity is not as such to be found in the New Testament” (2013b,8). The “fathers” of the late fourth century should beseen as “the giants on whose shoulders we need to stand”(10). In the second part of his book (chs. 11–20) Haskerinteracts with a number of Trinity theories, attempting to salvagewhatever is correct in them for use in his own three-self theory; heincorporates ideas particularly from Leftow, Craig, Rea, andSwinburne.

For Hasker, the Persons of the Trinity are three divine selves(Chapters 22–25). Against a modern Protestant trend, Haskerinsists that a doctrine of processions must be retained, arguing thatit enjoys “significant support” from scripture (217), andhe points out the awkwardness accepting “the main results of the[ancient] trinitarian controversy” while thinking that this“developmental process…had at its heart a fundamentallywrong assumption”, that is, that the Son and Spirit existbecause of the Father (222–23).

Hasker spends several chapters (25–28) addressing the question:“in virtue of what do the three persons constituteoneGod?” (203). The three enjoy some sort of unity of will andfellowship, and they are united in that the second and third exist andhave the divine nature because of the first, but such factorsdon’t, by themselves, imply that they somehow amount to a singlegod. Hasker holds that a crucial factor is the idea of their shareddivine nature as a concrete property or trope. Following Craig,sometimes Hasker characterizes this concrete divine nature as a divinemind or soul. He argues that for all we know, it is possible for onesuch trope of divinity “to support simultaneously three distinctlives” which belong to the Persons (228). He argues that thispossibility is indirectly supported by split-brain andmultiple-personality phenomena in human psychology. He takes these toshow that “It is possible for a single concrete humannature–a single trope of humanness–to supportsimultaneously two or more centers of consciousness” (236).

This supporting or sustaining relation, Hasker says, may optionally bespecified to involve the divine nature constituting each Person (ch.28).

We shall say, then, that the one concrete divine nature sustainseternally the three distinct life-streams of the Father, Son, and HolySpirit, and that in virtue of this the natureconstituteseach of the persons although itis not identical with thepersons. (244)

Constitution is defined here as asymmetric, so none of the Personsalso constitutes the divine nature (245). In a later discussion, heseems to make constitution central to the theory (Hasker 2018a).Adapting work on the metaphysics of material constitution by LynneRudder Baker, Hasker offers this definition:

Suppose x has F as its primary kind, and y has G as its primary kind.Then x constitutes y at a time t just in case at time t

x andy have all their parts in common,
x is inG-favorable circumstances
necessarily, if [an object]x of primary kindFis inG-favorable circumstances, [there is] an object[y] of primary kindG [that] shares all its partswithx, and
causal activity is required for there to be such aG, theform of activity depending on the natures ofF andG(Hasker 2024, 25; for previous formulations see Hasker 2018a,16–17, 2013b, 241–43; Howard-Snyder 2015b,108–9)

Applying this doctrine of non-material constitution to the Trinity, tosay that the divine nature constitutes the Father is to say that thedivine nature and the Father have all their parts in common and thatthe nature is in divine-Person-favorable circumstances. For a thing ofthe type “divine mind/soul or concrete nature” to be in“divine trinitarian Person”-favorable circumstances meansthat there is a divine trinitarian Person which has all his parts incommon with the first thing, and that it is conceivable that the firstthing exists even though there is nothing of the type “divinetrinitarian Person” that has all its parts in common with it.Hasker adds that in his view all the entities mentioned here aresimple (lacking proper parts), so each will be what metaphysicianscall an improper part of one another, satisfying condition i. (Thisclaim is problematic, since as normally definied an “improperpart” of x is identical with x; see theentry on Mereology, section 2.1. But for Hasker, the divine nature and each Person are non-identical.)Hasker also clarifies that the conceptual possibility in condition ivdoes not imply metaphysical possibility; Hasker denies that this ismetaphysically possible: the divine nature exists but no divine Personexists (2018a, 18). He adds that

The divine nature constitutes the divine trinitarian Persons when itsustains simultaneously three divine life-streams, each life-streamincluding cognitive, affective, and volitional states. Since in factthe divine nature does sustain three such life-streams simultaneously,there are exactly three divine Persons. (2018a, 17)

Presumably the divine-Person-favorable circumstances which the divinenature is in, is support of these life-streams.

Hasker argues that the “grammar” of the Trinity forbids aChristian from saying things like “three gods” based onthere being three Persons each of which is divine (2013b, 247). Again,although “God” in the New Testament nearly always refersto the Father, one can’t infer that the Father and God arenumerically one (248). With a nod to a mereological account of thePersons and God, he says that “Each Person is wholly God, buteach Person is not the whole of God” (250; cf. 257). Hasker alsoargues that the “Athanasian” creed can be read asnon-paradoxical if we realize that it is laying down rules about whatmust be said and what must not be said (250–54).

In the end, as with Swinburne, the Trinity which is called“God” is not literally a god, as it is not divine. ButHasker suggests that

in virtue of the closeness of their union, the Trinity is at timesreferred to as if it were a single person. The Trinity is divine,exhibiting all the essential divine attributes—not by possessingknowledge, power, and so on distinct from those of the divine persons,but rather in view of the fact that the Trinity consists precisely ofthose three persons and of nothing else. It is this Trinity which weare to worship, and obey, and love as our Lord and our God. (2013b,258)

In an attack on theories ofdivine simplicity, in which he sets aside considerations of God as Trinity, Haskerobjects that if God is simple, God is “dehumanized” inthat God must lack certain qualities which Christians should think Godliterally shares with human beings, such as caring for and beingresponsive to his creatures, and being able to either judge or forgivethem (2016, sec. 5). But while none of those qualities implies beinghuman, each arguably implies selfhood. Yet Hasker denies that God isliterally a self.

Brian Leftow points out the oddness of ascribing a soul to God theTrinity.

This [soul] is not God. It is not a Person either. It is some othersort of concrete divine individual. We had not suspected that a spiritcould have a soul; lo, God does! (Leftow 2018, 10)

Leftow also objects that the sentence “God is the ultimatereality” seems to be true by definition. But on Hasker’stheory, this soul (a.k.a. the divine nature), which is not God, wouldbe the ultimate reality, being the source of the Persons and so of God(the Trinity) (12). Again, Leftow objects that this theory is notmonotheistic; rather, the theory features three deities which wecan’t describe as such because there is one object (the divinenature/soul) which constitutes them (15).

Daniel Howard-Snyder objects that Hasker’s talk of the nature“supporting” or “sustaining” the lives or“life-streams” of the Persons is unintelligible (2015b,108–10). He also argues that it is unclear quite whatconstitutes the Persons, as in various places Hasker says that this isthe divine mind/soul, the concrete divine nature (a trope ofdivinity), and a single mental substance–and these would appearto be different claims (110). Also, monotheism uncontroversiallyimplies that there is exactly one god. But Hasker forbids saying thatany of the Persons is a god. And by definition being a god implieshaving the divine nature, and like others Hasker understands divinityto imply perfection in knowledge, power to intentionally act, andmoral goodness–thus, divinity implies being a self. This,Howard-Snyder says, is a necessary truth and one with which basicallyall Christians agree. But Hasker’s “God”, whetherthis is a community or a composite object, is not a self, and so isnot literally divine. But then, we’ve run out of candidates forbeing the only god; if neither the Father, nor the Son, nor the Spiritis a god, then it would seem that for Hasker there is no god!Anticipating monotheism-related objections, Hasker lobs variouscharges at Howard-Snyder (112–13), but in the end it seems thatHasker’s view is just that “God” can be spoken ofas if it were a self (114–15; 2024, 27). Taking a termfrom recent philosophy of mind, Howard-Snyder says that for Hasker Godis a “zombie”, a merely apparent self which in fact lacksany consciousness, any point of view and any mentality (114). Heconcludes that Hasker is not aiming for the sober metaphysical truthabout the Trinity but is instead settling for some sort of“as-ifery”. How, he asks, could it be more accurate todescribe God as “omnipotent and omniscient” than it is todescribe God as “powerless and ignorant” when onHasker’s account God is straightforwardly the latter? (115)

Hasker replies that his claim that the divine nature supports thelives of the Persons is no more unintelligible than is the claim that“my desktop computer supports word processing”; to supportis to “maintain in being or in action; to keep up, keepgoing” (Hasker 2018a, 11). Nor should it worry us that wecan’t understand how this supporting works (12).

A broadly similar theory is sketched by Joseph Jedwab (2022) using adifferent concept of constitution and the Neo-Lockean idea that factsabout persons exist because of more basic facts involving non-persons.Here each Person exists only because of God/the divine nature having acertain united stream of conscious experiences. “The fact thatthe Father exists is wholly constituted by the fact that God has thefirst total [experience] stream” (184). All of these experiences(from all three streams) have God as their subject but each streambelongs to a different Person. Unlike these Persons, God, beingperfect, must be fundamental (i.e. not exist because of anything else)(186). No Person on this account can be numerically identical withGod, but Jedwab argues that there is nonetheless a natural sense inwhich on this account each Person “is God”, namely, eachis wholly constituted by facts involving God (186–87). Jedwabalso extends the theory to include Incarnation.

2.5 Tri-personal Monotheism

William Lane Craig offers a model of how more traditionallytrinitarian claims might be coherently put together; his previousversion was called “Trinity Monotheism” (Moreland andCraig 2017, Craig 2006), but his revised model is called“Tri-personal Monotheism” (Craig 2024a). The maindifference between these is linguistic; before, Craig took “theTrinity” to be a singular referring term for the only god, butnow he understands “the Trinity” as a plural referringterm for the Father, Son, and Spirit. But the core of the new accountis the same:

We naturally equate a rational soul with a person, since the humansouls with which we are acquainted are persons. But the reason humansouls are individual persons is because each soul is equipped with oneset of rational faculties sufficient for being a person … Godis a soul which is endowed with three complete sets of rationalfaculties, each sufficient for personhood … God, though onesoul … [is] not one person but three, for God would have threecenters of self-consciousness, intentionality, and volition, as socialTrinitarians maintain. (Craig 2024a, 53)

This soul, for Craig, is the only god, the tripersonal God, but he nolonger calls this “the Trinity”. The Persons of theTrinity and the triune God are not “divine” in the samesense.

One way [to be divine] is by being an instance of the divine nature… there is only one such instance … the triune God. Butthe persons can be fully divine in some other way, such as sharing inthe concrete divine nature. Maybe they are metaphysically inseparableand overlapping parts of God. (2024c, 243)

Tuggy (2024b, 160) objects that such a soul would be only a singleperson whose personhood is twice over-determined, and that it isunclear how multiple persons would result from a soul being able tothink in three ways. But Craig (2024a, 53–54; 2024c,241–42) maintains that the view is clear and philosophicallyunproblematic, and that incoherence threatens a Trinity doctrine onlywhen statements that each Person “is God” are interpretedas statements of numerical identity. Against arguments that the NewTestament authors presuppose the numerical identity of the one Godwith the Father (alone) (Tuggy 2024a), Craig objects that this isimpossible because ancient people didn’t grasp, or didn’tclearly grasp, the concept of numerical identity (2024b, 203; 2024c,243). Tuggy replies that certain scriptural and creedal phenomena showthat they did, which is unsurprising, as it is normal for adult humansto have that concept (2024c, 260–61).

For several other objections to Craig’s previous theory, most ofwhich also apply to Tri-personal Monotheism, see Howard-Snyder2003.

Stephen Layman (2016) has constructed a similar and arguably betterdeveloped three-self Trinity theory. Motivated by the New Testament,Layman says that the three Persons of the Trinity are three selves(124–31). Each is “divine” in that he is a fittingobject of worship, and so is God the Trinity. God the Trinity isliterally a social entity, a concrete, primary substance which isstrongly analogous to a living thing, and which like a living thing isa self-maintaining event (149–50). “Strictly speaking,only the Trinity, the community of divine persons, is God, that is,ruler of all” (148). Yet the Persons are “of onesubstance” in that “each belongs to the kinddivinebeing”, where this means a Person which is a part of a god(150–51, 165–66).

One may object that a social entity can’t be a god, as such athing is merely an abstraction. Layman answers that social entitiesare concrete, not abstract, and can intentionally act (159–60).Intentionally acting requires having intentions, but social entitiesmay have these, even though they are not selves or even subjects ofconsciousness. Social entities may have intentions because their parts(i.e. various selves) have them. As a fallback, Layman suggests theview that social entities may act even though they’re incapableof intentional action (159). Layman argues that the Trinity can beomnipotent, perfectly good, and omniscient because its Persons are(160). Why then is the Trinity not a fourth divine person (see section3.1)?

In order to count as a person, an entity must be able to refer toitself rightly with the first-person singular pronoun “I”(or its equivalent). And the Trinity can not do this. (161)

But doesn’t the Bible portray God as a self who speaks in thefirst-person? Layman concedes that the Old Testament does. But becausethey believe in progressive divine revelation, Christians should readthe Old Testament as corrected by the New Testament. And in the NewTestament arguably there are “three divine persons (consciousbeings)”; Old Testament passages where “God” speaksfirst-person should be read as the Father speaking on behalf of theTrinity (164).

The account is not polytheism because only the Trinity is God, andbecause of the necessary unity of the three (160, 167). Butisn’t “Every divine person is a god” true bydefinition? No, because “divine” can mean relating to agod (without being a god), and in this common meaning the Persons ofthis theory are “divine”. Similarly, a hand can be“human” without itself being a human being (165).

How can the Son and Spirit be fully divine if each is caused by theFather and so does not exista se? Layman answers that“the objector’s intuition thatdivinity requiresaseity is not shared by those who drew up the [Nicene]creed” (167). Further, “it seems to me that aseity isclearly not essential to divinity, that is, it is not essential forbeing worthy of worship”. The qualities of omnipotence,omniscience, eternality, perfect goodness, and necessary existence aresufficient to guarantee the worship-worthiness of the Persons(168).

Like Swinburne Layman argues that a God who is a single self isimpossible. While aware than a theist may understand God to be“perfectly loving” in the sense of having a perfectdisposition to love which doesn’t have to be actualized, Laymannonetheless asserts that “There is … considerableplausibility in the claim that a truly solitary person who throughoutall eternity never expressed any love for anyone would not be aperfectly loving person” (153). Given that impossibility, sinceGod must be perfect independently of creation, “a truly solitaryperson would not be divine, for it would not be in love, perfectlyloving” (154). Additionally, Layman argues that it is“inconceivable” that a divine Person should flourishwithout loving another, and that surely only the love of finite selveswould not be enough (154–55). A solitary divine Person would be“an appropriate object of pity” (155). Again, Laymanargues that the Bible suggests that a divine Person must have not onlysplendor (exalted attributes) but also glory, “something atleast akin to fame–a kind of recognition, approval, orappreciation” which is conferred by another (156). A solitarydivine Person would be lacking this glory; but presumably a divinePerson must have glory. Thus, there couldn’t be just one divineperson (156–57). Layman is skeptical about philosophicalarguments purporting to show why there must be exactly three divinePersons, but he think’s he’s shown why there can’tbe only one. The limit of divine Persons to three, in his view, canonly come from the Bible (157–58).

2.6 Material Monotheism

Christopher Hughes (2009) suggests a theory much like the Constitutiontheory (section2.1.2 above) but without its controversial claim that there can benumerical sameness without identity. On this picture,

we have just one (bit of?) divine “matter,” three divineforms, and three (“partially overlapping,” materiallyindiscernible but formally discernible divine hylomorphs [compounds ofform and matter]…“divine person” is true of thethree hylomorphs, but…“God” is true of the (one andonly) (bit of?) “divine matter.” (2009, 309)

On this theory, “The Father is God,” means that the Fatherhas God for his matter, or that the Father is “materiatedby” God, and “The Father is the same God as the Son”means that these two are materiated by the same God(309–10).

An objection is that the one God of Christianity is not supposed to bea portion of matter. Hughes replies thatperhaps it isorthodox to say that God is a very unusual kind of matter (310).

Alternately, Hughes suggests a retreat from matter terminology, andargues that Persons of the Trinity can’t bear the same relationthey bear to one another that each bears to God. That is, itcan’t be correct, for example, that Father and Son areconsubstantial, and that the Father and God are consubstantial. Thereason is that for two things to be consubstantial is for there to besomething which both are “substantiated” or“ensubstanced” by. They are consubstantialbecause they both bear this other relation to a third,substantiating thing. Thus, e.g. “The Father is God” means“The Father is (a person of the substance) God.” Thus,even though Father and Son are numerically two, still it can be truethat “There is just one (substance) God” (311).

On this alternate view, though, what does it mean to say that God isthe substance of a divine Person? Hughes suggests that the case isanalogous to material objects. A sweater and some wool thread are“co-materiate” in that both are “materiated”or “enmattered” by one portion of matter, though they arenumerically distinct (311; cf. 313). Hughes suggests it is an openquestion whether this is a different theory, or just a restatement ofthe first “in more traditional theological terminology.”It will be the latter “If we can stretch the notion of‘matter’ far enough to cover God, and stretch the notionof material substance (aka hylomorph) far enough to cover the divinepersons” (312). Hughes ends on a Negative Mysterian note (seesection4.1 below), claiming that it is an advantage of this last account thatensubstancement is “a (very, though not entirely) mysteriousrelation” (313).

Leftow (2018) objects that this theory features four things which aredivine, which is at least one too many. Further, on this account Godhas but the Persons lack the divine attribute of aseity, which makesthe Persons “at best only second-class deities” (10).

2.7 Concept-relative Monotheism

Einar Bøhn (2011) argues that trinitarian problems ofself-consistency vanish when one realizes that the Trinity “isjust an ordinary case of one-many identity” (363). He takes fromFrege the idea that number-properties are concept-relative. Thus,

conceptualizing the portion of reality that is God as the Father, theSon, and the Holy Spirit, we have conceptualized it as being three innumber, but it is nonetheless the same portion of reality as what wemight conceptualize as God, and hence as being one in number.(366)
There is no privileged way of conceptualizing [this portion ofreality] in terms of which we can explain the other way. Both ways areequally legitimate. (369)

A difficulty for this approach is that most philosophers don’tthink there can be one-many identity relations, since identity is ofnecessity a one-one relation. Some allow there can be many-manyidentities; for instance, it may be that the three men who committedthe robbery are identical to the three men who were convicted of therobbery. Those who believe identity can be one-many typically do sobecause they accept the controversial thesis that composition (therelation of parts to a whole they compose) should be understood asidentity. Although Bøhn does accept that thesis (Bøhn2014), he argues that this Trinity theory relies only on our having“a primitive notion of plural identity” (2011, 371), thatis, a concept we understand without reference to any concept frommereological (parts and wholes) theory. For example, we can recognizea certain human body to be identical to a certain plurality of head,torso, two arms, and two legs. And we can recognize that a pair ofshoes is identical to a plurality of shoes (365).

Bøhn argues that orthodoxy, by the standards of either the NewTestament or the “Athanasian” Creed (see section5.3), requires that the Persons of the Trinity be distinct (i.e. no one isidentical to any other) but not that any is identical to the one God.Rather, orthodoxy requires that the one God is identical to the Threeconsidered as a plurality. Thus, e.g. “The Father is God”must be read predicatively, that is, not as identifying the Fatherwith God, but rather as describing the Father as divine (364, 367 n.13).

Does this theory make God’s triunity dependent on human thought?And might the divine portion of reality equally well be conceived asseventeen? Bøhn replies,

That numerical properties are relational properties with concepts astheir relational units is compatible with reality having a real andobjective numerical structure. (372)

Thus, it doesn’t follow that any conceptualization of thisportion of reality is equally correct. While in this context he demursfrom saying anything about concepts (372), it seems that Bøhnassumes in Fregean fashion that concepts are objective and notmind-dependent (Bøhn 2013, sec. 1).

Joseph Long (2019) objects that the theory is unorthodox because itrequires a type of thing which is divine and yet which is neither theTrinity nor any divine Person. Further, Bøhn’s talk of“portions of reality” is unintelligible. Finally,orthodoxy demands that the Persons of the Trinity “are one Godregardless of our conceptual scheme”, whereas on thisaccount whether or not the Persons are one god is relative to how weconceptualize them.

Sheiva Kleinschmidt (2012) argues that theories on which compositionis explained in terms of identity are of no use to the trinitarian,for such theories add no significant options to the options thetrinitarian already has.

3. Four-self, No-self, and Indeterminate Self Theories

Some Trinity theories don’t fit in to either one-self orthree-self categories, because they imply more divine selves thanthree, less than one, or are unclear about how many selves there mightbe in the Trinity.

3.1 God as a Functional Person

Chad McIntosh (2015) formulates a Trinity theory which is similar tothree-self theories except that it adds God the Trinity as a fourthdivine self. This theory is inspired by recent work by philosophers ongroup persons. It’s a longstanding part of legal tradition totreat various kinds of non-persons, such as corporations, as if theywere persons. This is particularly useful, e.g. in holdingcorporations responsible for damages they cause. But some philosophershave argued for group agency realism, the thesis that some groups ofpersons are themselves literal persons, with interests, knowledge,freedom, power to intentionally act, and moral responsibility(168–71). McIntosh distinguishes “intrinsicist”persons, persons which are so because of their nature, from“functional” persons, persons which are so because of howthey function. On this account the Persons of the Trinity areintrinsicist persons, while God the Trinity is a functional person(171).

McIntosh argues that since moral responsibility implies personhood (ofsome kind), and it is clear that the Trinity must be praiseworthy,e.g. “for having achieved salvation for humankind” or“just for having the character of a loving community”,then the Trinity must himself be a person. And it is widely agreed byChristians that the Trinity should be worshiped, but a non-personcan’t be a fitting recipient of worship (173).

One may object that the Christian God is supposed to be a Trinity ofPersons, not a Quaternity of Persons. As Leftow objects to anothertheory,

the very fact that the doctrine the Creed states is known as that ofthe Trinity militates against calling a four-[divine]-individuals vieworthodox. Had the Creed-writers envisioned God plus the Persons asadding up to four divine individuals, surely the doctrine would havebeen called Quaternity from the beginning (Leftow 2018, 10).

McIntosh replies that the tradition demands that there are exactlythree Persons (Greek:hypostaseis) which share the divinenature or essence, which is captured by his claim that there areexactly three intrinsicist Persons. This account doesnotclaim that God is a fourthhypostasis, a fourth intrinsicistPerson. Rather, God is a functional person, a Person not by hisessence, but rather who exists as a Person because of the unifiedfunctioning of the Father, Son, and Spirit (174).

McIntosh argues that the theory neatly sidesteps a number of commonobjections to three-self theories: here, God is a self and not merelya group or a composite object which is less than a self. In contrastwith three-self theories, as a literal self, personal pronouns may beliterally used of him. And this group which is a “he” canhave the divine attributes which imply being a self, such asomniscience and moral perfection. It also, McIntosh argues, eitherfalsifies or casts doubt on the key premise in Tuggy’s divinedeception argument against three-self theories (175–77, 180; seesection2.3.) Following some Old Testament scholars, McIntosh claims that ancientIsraelites recognized many groups, including their own nation, asliteral (group, functional) persons. He argues that this beliefexplains a number of oddities in the Old Testament, such as the ideaof group guilt, apparent beings which seem in some sense to beextensions of Yahweh’s personhood, and texts which switch easilybetween singular and plural subjects (177–80).

3.2 Temporal Parts Monotheism

H. E. Baber (2002) argues that a Trinity theory may posit the Personsas “successive, non-overlapping temporal parts of one God”(11). This one God is neither simple nor timeless, but is a temporallyextended self with shorter-lived temporally extended selves as hisparts. This does not violate the requirement of monotheism, because weshould count gods by “tensed identity”, which is“not identity but rather the relation that obtains betweenindividuals at a time,t, when they share a stage [i.e. atemporal part] att” (5). At any given time, only oneself bears this relation of temporal-stage sharing with God.

How can any of these selves be divine given that they are neithertimeless nor everlasting? Following Parfit’s work onpersonal identity, she argues that a self may last through time without being identicalto any later self at the later times; that is, “identity is notwhat matters for survival” (6). Each of these non-eternalselves, then, counts as the continuation of the previous one, and iseverlasting in the sense that it is a temporal part of an everlastingwhole, God. The obscure traditional generation and processionrelations are re-interpreted as non-causal relations between God andtwo of his temporal parts, the Son and Spirit (13–14). In alater paper, she argues thatany trinitarian may and shouldaccept this re-interpretation (Baber 2008).

Although Baber argues that this is a “minimally decent”Trinity theory, she admits that it is heretical, and names it a“Neo-Sabellian” theory, because on it, the Persons of theTrinity are non-overlapping, temporary modes of the one God (15; onSabellianism see section1.3). But the Persons in this theory are not mere modes; they are trulysubstances and selves, and there are (at least) three of them, thougheach is counted as the continuation of the one(s) preceding him. It isunclear whether the theory positsonly three selves(10–11). But she argues that the theory is preferable to many ofits rivals “since it does not commit us to relative identity orrequire anyad hoc philosophical commitments” (15), andeven though its divine selves don’t overlap, sense can be madeof, e.g. Jesus’s interaction with his Father (meaning not theprior divine Person, but God, the temporal whole of whom Jesus is atemporal part) (11–14).

This theory is notable in being a case not of rational reconstruction,but of doctrinal revision (Tuggy 2011). Many of its features arecontroversial, such as its unorthodoxy, its metaphysical commitmentsto temporal parts and the lasting of selves without diachronicidentity, its denials of divine simplicity and divine timelessness,and its redefinitions of “monotheism”,“generation”, and “procession”.

In a later discussion Baber argues that some form or other ofSabellianism about the Trinity is theoretically straightforward andfits well with popular Christian piety. Further, such theories cansurvive the common objections that they imply that God is onlycontingently trinitarian, and that they characterize God only inrelation to the cosmos. While some Sabellian theories do have thoseimplications, Baber argues that a trinitarian may just accept them(2019, 134–38).

Alternately, Baber (2019) develops a structuralist approach to theTrinity which doesn’t imply anything about how many selves itinvolves.

3.3 Persons as Relational Qua-Objects

Rob Koons (2018) constructs an account inspired by Aquinas, Augustine,and recent work on “qua-objects” by Fine and by Asher.Following the latter, Koons understands “qua-modifiednoun phrases as picking outintentional objects consisting oftropes or accidents, metaphysical parts of the base object”(346). Koons holds that even everyday objects imply the existence ofsuch intentional objects, i.e. things that can be thought. Thus, wecan distinguish Trump-qua-husband from Trump-qua-President; whilethese are real objects of thought, they both amount to beingproperties of Trump, which Koons thinks of as metaphysical parts ofDonald Trump.

Unlike most of the other theories in this entry, Koons builds his onthe foundation of divine simplicity, traditionally understood.According to this, God is numerically identical with his nature, hisone action, and his existence. God has no accidental (non-essential)properties and no proper parts, and he just is any essential propertyof his. In sum, God has no parts or components in any sense. While onemight suppose that this would rule out God being a Trinity, Koonsargues that to the contrary, we can understand how and why God is aTrinity by “locating God in an extreme and exotic region oflogical space” (339).

The divine nature just is any divine attribute, e.g. omnipotence. Inaddition, Koons argues that the divine nature just is “anintentional relation: namely, perfect knowledge and perfectlove.”. Understanding or knowledge generally should beunderstood “as aninternal relation between the mindand its external object.” (340).

Following Aquinas, Koons says that God (a.k.a. the divine nature)understands all things through himself; God is essentially omniscientand essentially self-understanding. Thus, the divine nature impliesthe existence of three relational qua-objects, which are the Personsof the Trinity. These are not merely three ways we can think of God,or three ways God may appear to us, but rather these objects resultfromGod’s essential self-understanding (345). Each ofthese four things–God (the divine nature), the Father, the Son,and the Spirit–has the divine nature as its one metaphysicalcomponent, and each has all the divine attributes (346). Each of thosefour is numerically distinct from each of the three others (347).

The theory requires more than the relation of (absolute) numericalsameness or identity. In addition, Koons defines a relation of“real” sameness. Like identity, this relation is reflexiveand symmetrical, but unlike identity it is neither transitive norEuclidean (such that if any x is related to some y and to some z thenthis implies that y and z are related in that same way). Thus, realsameness is not an equivalence relation (348, 357 n. 5) According tothis theory each Person is really the same as the divine nature (God),but not identical to him. But no Person here is really the same as anyother Person; all three are really distinct from one another. Tosummarize: there are four divine realities on this model of theTrinity. The three Persons are so many qua-objects, while God is not.None of these four is really distinct from God; all are really thesame as him. Yet none of the four is identical to any of the others(348).

One may ask why there should be only three qua-objects here, whenobjects like a human person or an apple, having many properties, mightimply hundreds or thousands of qua-objects. The answer is that notevery qua-object of God is a divine Person. Many such, Koons says, arecontingent, e.g. God-as-creator, or God-as-friend-of-Abraham; suchwould not have existed had God not created. And any qua-object of Godwhich involves only an essential property of his, e.g.God-as-omnipotent, is numerically identical to God (345). To be a“hypostatic qua-object” (i.e. a God-as-thing which is adivine Person) something must exist necessarily, be numericallydistinct from God, and be such that “It is not wholly groundedin a logical or conceptual way on any other divinequa-objector objects. So, it must be fully determinate (non-general,non-disjunctive, and non-negative) in its definition” (346).This last condition is meant to prevent the proliferation of divinequa-objects (354–56). Koons argues that this account explainswhy there are exactly three divine Persons.

My main claim is that, as a matter of metaphysical necessity, thereare exactly three hypostaticqua-objects (namely, Father,Son, and Spirit, as defined above). This is because there are only twointrinsic, relational properties of God (knowing and being known), andthese give rise (on purely logical grounds) to only threenon-disjunctive combinations. (346)

Divine love doesn’t imply further Persons because it’s thesame relational property as divine self-knowing. God-as-knowerisn’t numerically the same as God-as-known because of theessential asymmetry of the knowing relation. Divine love, Koons says,is a kind of charity or friendship; thus, lover and belovedcan’t be numerically identical. So if the Father loves the Son,this implies that they are numerically distinct (non-identical). Italso implies that they are really distinct and not really the same. Inspecifying what he means by real distinctness Koons writes,

Twoqua-objects with the same ultimate base are reallydistinct if and only if they are numerically distinct and thedistinction between them isintrinsic to their ultimate base.(348)

The distinction between these qua-objects Father and Son is intrinsicto their ultimate base, God (the divine nature) because he is theintrinsic yet relational property of love (348–49). This has theconsequence that “the divine nature cannot love or be loved byany of the divine Persons” (351).

Koons argues that this theory has many advantages over some rivals.Against the constitution based three-self theory of Brower and Rea(see section2.1.3), it allows for divine simplicity, as the Trinity does not involve anymetaphysical components or parts other than the divine nature. And heclaims that their account amounts to tritheism, “since eachPerson is divine in His own unique and incomparable way”. Incontrast, on Koons’s theory, “each of the three Persons isdivine in the same way–simply by being a divinequa-object, and the divine nature is complete and fullydivine in itself”. Again, Koons’s theory can, and theirscan’t, explain why there are exactly three divine Persons. Andtheir theory requires three different odd and hard to explain personalattributes (352). As contrasted with any “social” theory,this one doesn’t have divine Persons which are really distinctfrom the divine nature (God) (353).

Koons recognizes that many will object that this theory istetratheism; it features four realities, each of which is divine;prima facie, these would be four gods. Koons believes that the realsameness of each of the Persons with God should rule out anypolytheism and rule in monotheism. He offers this definition ofmonotheism:

There is one and only one thing such that no divine being is reallydistinct from it (348).

This is equivalent to:

There is one and only one thing such that every divine being is reallythe same as it.

But a “divine being” is a god. Thus the meaning of thisdefinition can be restated as:

There is one and only one thing such that every god is really the sameas it. Or: There is one and only one thing such that no god is reallydistinct from it.

This is a controversial definition; one may think that Koons simplyredefines “monotheism” as compatible with any number ofgods greater than zero. Put differently, one may count things byidentity. Why can’t one also count gods in this way? Again, if ais a god, and b is a god, and they are non-identical, what is it about“real sameness” that implies that they’re really thesame god? Why isn’t this anad hoc, theory-savingdefinition?

One may wonder here how the four realities can be equally divine. Itwould seem that whereas God (the divine nature) would not existbecause of any other, and so would exista se, each of thequa-object persons would exist because of God, their base.Wouldn’t this make God greater than each of the Persons? Again,on this account each of these four is intrinsically and essentiallydivine, yet the Persons can love, while God can not. How then can allfour be omnipotent?

Some will judge this theory to inherit all the problems of thetraditional divine simplicity doctrine it assumes. Others willconsider its fit with simplicity to be a feature and not a bug. Koonspoints out that it also assumes constituent ontology, a Thomisticaccount of thought, and the claim that the divine nature is anintentional relation (356).

3.4 Persons as Improper Parts of God

An account of the Trinity by Daniel Molto tries to preserve the ideafound especially in Western creeds that “each divine person is,in some sense, all of God” (2018, 395). (Because of this heclaims the title “Latin” for the theory.) He employs anon-standardmereology (theory of parts and wholes) to interpret what he considers to be thethree requirements for a Trinity theory: that there’s only onegod, that no Person of the Trinity is identical to any other, and thatin some sense it is true that each Person individually “iswholly” God (400). The view is that God, the Father, the Son,and the Spirit are all improper parts of one another, while none isnumerically identical to any other. This is shown in the followingchart; the lines represent the symmetrical and transitive improperparthood relation.

A representation of the divine persons and the Trinity as improper parts of one another.

On more “classical” mereological systems, if A is animproper part of B, this implies that A and B are numericallyidentical, but in the system suggested by Molto, this is denied. Heargues that this change is not merely theologically motivated, but maybe applicable to other issues in metaphysics (410–13).

Molto discusses a problem for the model which arises from thetransitivity of parthood and the axiom that things which are improperparts of one another must have all their proper parts in common. Ifthe body of the incarnate Son is a proper part of him, then givenMolto’s model of the Trinity, this body would also have to be aproper part of God, of the Father, and of the Holy Spirit –claims which most Christian theologians would reject. In response, headds three further elements to the model, as shown here:

A mereological representation of the Trinity as in Molto's mereological one-self Trinity theory.

Here, D = the divine nature of the Son, N = the human nature of theSon, and B = the body of the Son. As before, the lines with arrows oneach end represent the symmetrical improper parthood relation. In thisillustration the one-arrow lines represent the asymmetricalproper parthood relation. Thus, the divine nature of the Sonand the human nature of the Son are proper parts of the composite Son,and the human body is a proper part of the human nature (and thus,also of the composite Son).

Molto leaves it up to theologians whether this sort of theory isorthodox (514–17). His suggestion is only that this may be asimpler and less controversial solution to the logical problem of theTrinity, that is, to showing how trinitarian claims do not imply acontradiction (397–98, 416–17).

4. Mysterianism

The core meaning of the ancient Greekmysterion is somethinghidden or secret, especially religious rites which are accessible onlyto the select few. In the New Testament, a “mystery” isusually a formerly hidden thing which has now been divinely revealed(Toulmin 1807). But in time Christians came to describe theirsacraments as “mysteries” in the older sense, and oftennowadays to call some thing or doctrine a “mystery” is tocelebrate it as holy and valuable.

But there is also a long tradition of claiming that the Trinitydoctrine, rightly understood, is in some sense a mystery, somethinghidden or formerly hidden. There are four non-exclusive meanings here.First, to say this doctrine is a mystery is to say that it isunknowable apart from divine revelation, by far a majority view amongtrinitarians. Second, that the Trinity is a “mystery” maybe to say that it is to some degree unexplainable. While sometrinitarians have attempted to explain some facts about the Trinity,e.g. why there must be more than one divine Person (see section2.3 above), it is uncontroversial that many aspects of it are presentlyunexplainable by us, e.g. why does the Father spirate the Spirit, butgenerate the Son? Any theist, trinitarian or not, will hold that thereis quite a lot about God which can’t be explained, but of coursethis is also true of stars, viruses, and birds. Third, to say thatthis doctrine is a mystery may be to say that the meanings of itssentences are to some degree hidden from us, so that the doctrine isto some degree unintelligible. While they are in principle fullyunderstandable (presumably God understands them), our present limitsrender them only partially understandable by us. Fourth, to say thatthe Trinity is a mystery may be to say that it appears to imply one ormore contradictions; the truth, in a sense, is hidden from us by thisappearance of incoherence, which on the assumption that allcontradictions are false and not true, is the appearance of falsehood.Generally, but not always, the idea here is that our currentlimitations are responsible for this appearance; in principle, one maysee how the claims are coherent after all, and so perhaps in the nextlife this veil will be removed.

These last two senses of “mystery” have been widelydeployed in accounts of the doctrine of the Trinity. Normally it is astrike against a theory if it contains hard to understand claims orseeming contradictions. But the Mysterian urges that thesedifficulties are to be expected given God’s greatness and ourpresent limits; it would be a mistake to expect either clarity orseeming coherence. Intellectual humility demands that we accept eitheror both. This entry describes those who claim the Trinity doctrinecontains sentences which to some degree can’t be understood asNegative Mysterians, while those who urge that it seems to imply oneor more contradictions are Positive Mysterians.

A difficulty with both approaches is: how can we be sure that theseproblems are thrust on us by the evidence and are not the product ofour own speculative mis-steps? Neither partial unintelligibility norseeming incoherence seem to follow simply from the idea of a muchgreater God revealing himself to mere humans. Why couldn’t anall-knowing and all-powerful being carefully curate the revealedinformation so as to avoid both problems, with or without bolsteringour cognitive capacities? Again, how would one know the limits ofhuman understanding, or that one has reached them? One answer to theseconcerns is that the failure of even great theologians so far to finda mystery-free model of the Trinity makes it likely that such a modelis impossible for us in this life (Vohánka 2013b,86–89).

At its extreme, a Mysterian may hold that no first-order theory of theTrinity is possible, so we must be content with delineating aconsistent “grammar of discourse” about the Trinity, i.e.,policies about what should and shouldn’t be said about it. Inthis extreme form, Mysterianism may be a sort of sophisticatedposition by itself—to the effect that one repeats the creedalformulas and refuses to explain how, if at all, one interpretsthem.

More common is a moderate form, where Mysterianism supplements aTrinity theory which has some understandable content, but which isvague or otherwise problematic. Thus, Mysterianism is commonly held asa supplement to one of the theories of sections 1–3.

Christian unitarian views on the Father, Son, and Spirit are typicallymotivated in part by hostility to Mysterianism. (See the supplementarydocument onunitarianism.) But the same can said of many of the theories of sections1–3.

Sophisticated modern-era Mysterians include Leibniz and the theologianMoses Stuart (1780–1852). (Antognazza 2007; LeibnizTheodicy, 73–122; Stuart 1834, 26–50.)

4.1 Negative Mysterianism

In the late fourth-century pro-Nicene consensus Negative Mysterianismtakes the form of refusing to state in literal language what there arethree of in God, how they’re related to God or to the divineessence, and how they’re related to each other. (Seesection 3.3 in the supplementary document on the history of Trinity theories.)The Persons of the Trinity, in this way of thinking, are somewhat likethree men, but also somewhat like a mind, its thought, and its will,and also somewhat like a root, a tree trunk, and a branch. Multipleincongruous analogies are given, the idea being that a minimal contentof the doctrine is thereby expressed, though we remain unable toconvert the non-literal claims to literal ones, and may even be unableto express in what respects the analogies do and don’t fit.Negative Mysterianism goes hand in hand with the doctrines of divineincomprehensibility (that God or God’s essence can’t beunderstood completely, at all, or adequately) and divine ineffability(that no human concept, or at least none of some subset of these,applies literally to God). Some recent studies have emphasized thecentrality of Negative Mysterianism to the pro-Nicene tradition oftrinitarian thought, chastising recent theorists who seem to feelunconstrained by it (Ayres 2004; Coakley 1999; Dixon 2003).

The practical upshot of this is being content to merely repeat theapproved trinitarian sentences. Thus, after considering and rejectingas inadequate multiple analogies for the Trinity, Gregory of Nazianzusconcludes,

So, in the end, I resolved that it was best to say“goodbye” to images and shadows, deceptive and utterlyinadequate as they are to express that reality. I resolved to keepclose to the more truly religious view and rest content with some fewwords, taking the Spirit as my guide and, in his company and inpartnership with him, safeguarding to the end the genuine illuminationI had received from him, as I strike out a path through this world. Tothe best of my powers I will persuade all men to worship Father, Son,and Holy Spirit as the single Godhead and power, because to him belongall glory, honor, and might forever and ever. Amen. (Nazianzus,Oration 31, 143.)

Often a Negative Mysterian will say that the Trinity doctrine enablesus to knowthat but nothow God is triune(Vohánka 2013b, 83–84). Oliver Crisp (2019) sets forth aTrinity doctrine which is thin in content. Specifically,

The terms “person” and “essence” …demarcate the way in which God is three and the way in which God isone … [they] are referring terms that are placeholders; we donot have a clear conceptual grasp on their semantic content. (100)

Nonetheless this theory is “the best explanation given the dataof Scripture and the testimony of the earliest witnesses to theapostolic message” (85).

Jean-Baptiste Guillon (2022) argues that coherence concerns are adistraction from the harder problem of how believers can assign anymeaning at all to traditional trinitarian sentences. He proposes anaccount based on experiences available even to laypeople(194–99).

Opponents of this sort of mysterianism object to it as misdirection,special pleading, neglect of common sense, or deliberate obfuscation.They emphasize that trinitarian theories are human constructs, and adesideratum of any theory is clarity. We literally can’t believewhat is expressed in trinitarian language, if we don’t have agood enough grasp of its meaning, and to the extent that wedon’t understand it, it can’t guide our other theologicalbeliefs, our actions, or our worship (Cartwright 1987; Dixon 2003,125–31; Nye 1691b, 47). Negative Mysterians reply that it iswell-grounded in tradition, and that those who are not naivelyoverconfident in human reason expect significant unclarity in thecontents of this doctrine.

4.2 Positive Mysterianism

The Positive Mysterian holds that trinitarian doctrine, rightlyunderstood,seems to imply one or more contradictions; thehuman mind is adequate to understand many truths about God, althoughit breaks down at a certain stage, when the most profound divinelyrevealed truths are entertained. Sometimes an analogy with recentphysics is offered; if we find mysteries (i.e., apparentcontradictions) there, such as light appearing to be both a particleand a wave, why should we be shocked to find them in theology (vanInwagen 1995, 224–27)?

The best-developed Positive Mysterian theory is that of James Anderson(2005, 2007), who develops Alvin Plantinga’s epistemology (andlater Michael Huemer’s phenomenal conservatism, Anderson 2023)so that beliefs in mysteries (merely apparent contradictions) may berational, warranted, justified, and known. Orthodox belief about theTrinity, Anderson holds, involves believing, for example, that Jesusis identical to God, the Father is identical to God, and that Jesusand the Father are not identical. Similarly, one must believe that theSon is omniscient but lacks knowledge about at least one matter.These, he grants, areapparent contradictions, but for thebeliever they are strongly warranted and justified by the divinetestimony of Scripture. He argues that numerous attempts by recenttheologians and philosophers to interpret one of the apparentlycontradictory pairs in a way that makes the pair consistent alwaysresult in a lapse of orthodoxy (2007, 11–59). He argues that theChristian should take these trinitarian mysteries to be“MACRUEs”, merely apparent contradictions resulting fromunarticulated equivocations, and he gives plausible non-theologicalexamples of these (220–25).

It is plausible that if a claim appears contradictory to someone, shethereby by has a strong epistemic “defeater” for thatbelief, i.e., a further belief or other mental state which robs thefirst belief of rational justification and/or warrant. A stock exampleis a man viewing apparently red objects. The man then learns that ared light is shining on them. In learning this, he acquires a defeaterfor his belief that the items before him are red. Thus with theTrinity, if the believer discovers an apparent contradiction in herTrinity theory, doesn’t that defeat her belief in that theory?Anderson argues that it does not, at least, if she reflects properlyon the situation. The above thought, Anderson argues, should becountered with the doctrine of divine incomprehensibility, which saysthat we don’t know all there is to know about God. Given thistruth, the believer should not be surprised to find herself in theabove epistemic situation, and so, the believer’s trinitarianbelief is either insulated from defeat, or if it’s already beendefeated, that defeat is undone by the preceding realization (2007,209–54).

Dale Tuggy (2011) argues that Anderson’s doctrine of divineincomprehensibility is true but trivial, and not obviously relevant tothe rationality of belief in apparent contradictions about God. Theprobability of our being stuck with such beliefs is a function notonly of God’s greatness in comparison to humans’ cognitivepowers, but also of what and how much God chooses to reveal abouthimself. Nor is it clear that God would be motivated to pay the costsof inflicting apparently contradictory divine revelations on us.Moreover, Anderson has not ruled out that the apparent contradictionscome not from the texts alone, but also from our theories orpre-existing beliefs. Finally, he argues that due to the comparativestrength of “seemings”, a believer committed to paradoxeslike those cited above will, sooner or later, acquire an epistemicdefeater for her beliefs.

In a reply, Anderson (2018) denies that divine incomprehensibility istrivial, while agreeing that many things other than God areincomprehensible (297). While Tuggy had attacked his suggestions aboutwhy God would want to afflict us with apparent contradictions,Anderson clarifies that

my theory doesn’trequire me to identify positivereasons for God permitting or inducing MACRUEs. For even if I concedeTuggy’s point that “the prior probability of God inducingMACRUEs in us is either low or inscrutable,” the doctrine of[divine] incomprehensibility can still serve as…an undercuttingdefeater for the inference fromD appears to be logicallyinconsistent toD is false. (298–99)

The defense doesn’t require, Anderson argues, any more than thatMACRUEs are “not very improbable given theism”(299). As to whether these apparent contradictions result from thetexts rightly understood, or whether they result from the textstogether with mistaken assumptions we bring to them, this is aquestion only biblical exegesis can decide, not anya prioriconsiderations (300). As to Tuggy’s charge that a believer intheological paradoxes will inevitably acquire an undefeated defeaterfor her beliefs, Anderson argues that this has not been shown, andthat Tuggy overlooks how a believer may reasonably add a relevantbelief to her seemingly inconsistent set of beliefs, such as that theapparently conflicting claims P and Q are only approximately true, orthat “P and Q are the best way for her to conceptualize mattersgiven the information available to her, but they don’t representthe whole story” (304).

Anderson’s central idea is that the alleged contradictions ofChristian doctrine will turn out to bemerely apparent. Incontrast, a few theologians have held that the true Trinity doctrineimplies not merely apparent but also real contradictions. Such holdeither that there are exceptions to the logical law ofnon-contradiction or that there is no such law. (See the entry oncontradiction.) While some philosophers have argued on mostly non-religious groundsfordialetheism, the claim that there can be true contradictions, this position hasfor the most part not been taken seriously by Christian theologians,although it has popped up here and there as an extreme minority report(Anderson 2007, 117–26; Lourié 2019a, 2019b).

4.3 Contradictory Mysterianism

Logician Jc Beall (2023a) vigorously defends a version of the doctrineof the Trinity on which there are apparent and real contradictions,claims which are both true and false. “The full truth about Godcontains falsehoods; for the full truth is contradictory”(2023a, 95). Johnson and Molto (2023) have argued that contradictionsare well-suited to be what Roman Catholic tradition means by“mysteries” in the strictest sense of the term. Beall doesnot lead with the idea of mystery, but his account acknowledges a“familiar experience of mystery” when attempting tosimultaneously think and believe, for example, that it’s truethat Christ is God and it’s false that Christ is God (Beall2023a, 79). Given that logic itself dosen’t rule out truecontradictions, in Beall’s view the unsuccessful project ofaccurately consistentizing this doctrine should be given up(99–130).

Building on his earlier work, this account assumes that “Christis a contradictory being, one of whom some contradictions aretrue” (2023a, 4; Beall 2021), that theology aims at truth and sois subject to logic (2023a, 5–8), that there is only one god,the triune God (8–11), and that the “Athanasian”creed specifies “the ‘axioms’ (so to speak) oftrinitarian reality” (9). That creed, read in a “simple,flat-footed — and charitable” way, requires:

1. “the divine persons are pairwise distinct (i.e.,non-identical).”
2. “each divine person is (identical to) God.”
3. “the number of gods is 1 (viz., God).” (10)

These Persons’ divinity is not of any lesser sort;“being divine is no more nor less thanbeingidentical to God” (12).

Beall holds that logic itself does not include any identity relation;any theory has to specify what sort of identity relation(s) itrecognizes (Beall 2023a, chs. 2–3). The above axioms aresupposed to motivate the view that the trinitarian identity relationis non-transitive; since each Person is (in the special, trinitariansense) identical to God yet no Person is identical to any other, theargument of section1.4 above must be invalid. Using his preferred account of logicalentailment (ch. 2) and what he calls a “leibnizian recipe”for defining identity relations (44–51), such“identity” relations are defined, roughly, asindistinguishability regarding a certain range of non-identitypredicates in a theory (44–46). Adding the assumption that therecan be true contradictions, Beall employs that recipe to define aspecifically trinitarian concept of identity which is non-transitive(51–52). Thus, when it is understood that the sort of identityis this specifically trinitarian kind, the argument of section1.4 above is invalid at steps 8, 10, and 12.

The account requires three contradictions employing that specificidentity concept: the Father is identical to God and it’s notthe case that the Father is identical to God, the Son is identical toGod and it’s not the case that the Son is identical to God, andthe Holy Spirit is identical to God and it’s not the case thatthe Holy Spirit is identical to God (Beall 2023a, 63–78).God’s threeness or tri-unity is God’s identity with eachof Father, Son, and Holy Spirit (40). God’s oneness is theidentity of each of those with God (70). Partial counting conventionsare specified which imply the following counts: one triune being, onetriune god, three divine Persons, and one omnipotent thing(60–66, 86–87).

Beall argues that this contradictory account is better motivated thanits coherence-aimed rivals, and that it betters them in severaltheoretical virtues, including simplicity, metaphysical andepistemological neutrality, and providing a unified solution to bothIncarnation and Trinity (chs. 4–5; Beall 2021, corrected byBeall 2023a, 91–94).

Beall has addressed many objections (Beall 2019, 418–30; 2021,ch. 4; 2023a, ch. 5; 2023b ). Probably the hardest are based onChristian tradition; neither the Bible nor the patristic mainstream(Reese 2023) seem to be intentionally putting forward a contradictorydoctrine of God. Again, Christian tradition does not allow assertingthe falsity of statements like “The Father is God” and“The Son is God,” which this theology requires (eventhough on this account both are also true) (Kilby 2024; see thereplies in Beall 2023, 94–95 and 2024).

Scott Williams (2024) objects that by identifying each Person with Godthe account is heretical modalism, and that since the specifiedidentity relation is symmetrical, “The Father is God”implies “God is the Father,” which is contrary to therequirements of the “ecumenical councils” (26).

5. Beyond Coherence

Analytic literature on the Trinity has been laser-focused on thelogical coherence of “the” doctrine, addressing animagined critic arguing that the doctrine is clearly incoherent. Theydefend it by suggesting models of the Trinity, intelligible andarguably coherent interpretations of most or all of the traditionallanguage. But in recent work the tools of analytic philosophy havealso been applied to several closely related issues.

5.1 “The Trinity” and Tripersonality

The term “Trinity” has been used either as a singularreferring term or as a plural referring term (Tuggy 2020). Thefirst usage goes hand in hand with the claim that the one God just isthe tripersonal God, the Trinity. But the earlier use of“Trinity” (Greek:trias, Latin:trinitas)–where that term refers to a“they” and not a “he” or an“it”–still survives, and some Trinty theories implythat the term “Trinity” refers only in this way.

Most statements of faith by trinitarian Christian groups and mosttheologians seem to assume or imply that the Trinity just is God (andvice-versa); the only god is the tripersonal God, the Trinity, thus“Trinity” is normally a singular referring term denotingthat reality. This God, it is assumed, does not merely happen to betripersonal, but must be so; on such a view, it looks liketripersonality will be an essential divine attribute. Thus, it canseem axiomatic that “Christians hold that God is Trinitarian inGod’s essential nature” (Davis and Yang 2017, 226). SomeTrinity theories embrace this (section2.5). However, if this is so, it is hard to see how each of the Personscould be divine in the way the one God is divine, since generallytrinitarians don’t want to say that each Person is tripersonal.(See section2.1.5 for an exception.)

Thus, some purported Trinity theories eschew a thing which istripersonal, while affirming three divine Persons whose divinity doesnot require tripersonality (sections2.1.3,2.1.4). For such theories, “Trinity” is a pluralreferring term. Joshua Sijuwade (2021a, 2021b) and Beau Branson (2022,2024b) have argued for a “Monarchical Trinitarianism” onwhich there is no tripersonal god, but rather the unique god isidentical with the Father alone, although the other two Persons arefully divine and can be called “God.” Branson (2024a)argues that because the Son and Spirit are inseparable from the Fatherthey should be counted as one god.

Steven Nemes’s “post-catholic doctrine of theTrinity” is despite the name a non-standard unitarian theology,on which God the Father is the one God, who is “Realityitself” such that all other things are his self-caused modes(2023, chs. 5, 7). What is triadic, according to Nemes, is how God isexperienced, as “the World-Whole … the particular Object[i.e. various finite things we experience] … and as theabsolute Life which gives one to oneself in life” (202). Jesus,the human Son of God not one of those three, but is rather understoodalong the lines of a spirit-Christology, God empowering a real humanMessiah, by his spirit (ch. 6).

5.2 Logic Puzzles and Language

While many discussions start with claims that are seen as the heart ofthe “Athanasian” creed, a recent piece by Justin Mooney(2018, 1) starts with this seemingly inconsistent triad of claims:

God is triune.
The Son is not triune.
The Son is God.

Dale Tuggy (2014, 186) presents this inconsistent triad.

The Christian God is a self.
The Christian God is the Trinity.
The Trinity is not a self.

One-self and four-self trinitarians deny 3, and three-selftrinitarians deny 1. But Tuggy argues that for scriptural reasons aChristian should deny 2. (See also section5.4 and the supplementary document on the history of trinitariandoctrines,section 2.)

Ryan Byerly (2019) explains “the philosophical challenge of theTrinity” as centering on the key Nicene term“consubstantial” (Greek:homoousios). How can thethree Persons be “consubstantial” so that each equally insome sense “is God”, where this implies neither theirnumerical identity, nor that there’s more than one god?

Jedwab and Keller (2019, 173) see the fundamental challenge for theorthodox trinitarian as showing how this seemingly inconsistent triadof claims is, rightly understood, consistent:

There is exactly one God.
There are exactly three divine Persons.
Each divine person is God.

They argue that this must involve paraphrases, clearer formulations of1–3 which can be seen as possibly all true. They compare how thetheories of sections2.1,2.3, and1.5 above must do this, and conclude that it is easier for the first ofthese to provide paraphrases which plausibly express the same claimsas the originals, which is a point in favor of such relative identitytheories.

Beau Branson (2019) explores these claims as constituting “thelogical problem of the Trinity”: each Person “isGod”, they are distinct from one another, and yet there is onlyone thing which “is God”. These provide materials for aformidable argument against any doctrine that entails those sevenclaims. He argues that all possible non-heretical solutions to thatproblem either equivocate on the predicate “is God”(roughly: what are called “social” theories, discussed insections 2.2–7) or insist that divine Persons must be counted bysome relation other than “absolute” or“classical” identity (i.e. relative identity theories asdiscussed in section2.1).

Another recent piece compares different approaches to the Trinity byhow they respond to an anti-trinitarian argument based on allegeddifferences between the Father and the Son (Tuggy 2016b).

Steven Nemes (2023, ch. 3) poses a four-way destructive dilemma fortrinitarians, arguing that a Trinity doctrine clashes with othertheological commitments of catholic Christianity whether (1) thePersons are ontologically prior to the essence, (2) the essence isontologically prior to the Persons, (3) the Persons are the essenceare distinct but “coeval” (on the same ontological level),(4) the Persons just are the essence.

5.3 Foundations

A tradition going back at least to Cartwright (1987) is using thelanguage of the so-called “Athanasian” creed to generatecontradictions, the task of the philosophical theologian then being toshow how these can be avoided by more careful analysis. This Latindocument is by an unknown author and is not the product of any knowncouncil. Modern scholarship places it well after the life ofAthanasius (d. 373) and sees it as influenced by the writings ofAugustine (Kelly 1964).

Objecting to making it a standard of trinitarian theology, severalauthors have pointed out its dubious provenance and coherence, andhave observed that it has mainly been accepted in the Western realmand not in the East, and that it seems to stack the deck againstthree-self theories (Layman 2016 136–37, 169–71; McCall2003, 427). Williams argues that it fails to adequately express thetrinitarian doctrine of the “ecumenical” councils, onwhich see below (2022b, 354–56; 2024, 21). Tuggy (2016b) objectsthat starting with this problematic creed causes analytic theologiansto neglect the question of if and how the teaching of this creed isthe same as various statements from the “ecumenical”councils, pre-Nicene theologies, or the Bible. But William Haskerargues that rightly understood, the claims of this creed may not beparadoxical, as it is largely concerned with what may and may not besaid (2013b, 250–54). Often overlooked is the fact that a RomanCatholic council and Pope endorsed it in 1439 (Tanner 1990,550–53 ).

Apart from the “Athanasian” creed, H.E. Baber describesfive different foundations for theorizing about the Trinity, endorsingthe fourth.

This poses the question of what the ‘foundations’ for thephilosophical investigation of Trinitarian theology should be if it isnot either [1] the declarations of Church councils or [2] thetheological works of the Fathers or [3] Scripture which…doesnot include any Trinitarian doctrine…what philosophicaltheology should be about…[is] [4] the discourse and practice ofthe Church, and by that I do not mean [5] the doctrinal claims of theChurch in its pretension to being a teaching institution, but [4] theliturgy, hymnody, and art, customs and practices, religious objectsand religious devotions which, together, constitute the Christianreligion and its practice. The aim of philosophical theology is tomake sense of the discourse and provide a rationale for the practiceswhile avoiding logical incoherence. (Baber 2019, 186–87)

Some in the literature fall cleanly into one of Baber’scategories, but more commonly, work in analytic theology is done whileleaving unclear just what are the foundations of trinitariantheorizing.

Timothy Pawl (2020) and Scott Williams focus on the teachings of theseven “ecumenical” councils, which arguably specifytrinitarian language required by all catholic traditions. Williams(2022b, 2024) has shown that giving an ecumenical-council-friendlyaccount of the Trinity is harder than many suppose, since the sixthecumenical council (Constantinople III, 680–81) demands thatamong the Trinity, because of the shared divine essence, inWilliams’s summary, “each divine action-token is shared bythe three divine hypostases, and it is not the case that one and onlyone divine hypostasis can perform one action-token” (2022, 343).This arguably rules out most three-self theories, on which each Personhas his own mind, power, and will; see section2 above, especially 2.1.4.

In favor of Baber’s second approach, Beau Branson (2018)critiques what he calls “the virtueapproach”–basically, treating theological issues likemetaphysical or logical puzzles calling for creativetheorizing–as point-missing, question begging, and unclear. Incontrast, he advocates for “the historical approach”,which assumes that the content of “the doctrine of theTrinity” should be considered as fixed by the views of“mainly various fourth-century theologians” (sec. 4). Itis misguided, he argues, to focus merely on the theoretical virtues ofvarious rational reconstructions of what traditional Trinity languageis really supposed to be expressing, as most of these will notplausibly be expressingthe historical doctrine. New-fangledaccounts, Branson argues, have a burden of showing how they, ifcoherent, imply that the historical doctrine of the Trinity iscoherent, and indeed why the former should even count as a version ofthe latter (sec. 5). (Similarly with other theoretical virtues.) Atany rate, nothing about the project of analytic theology requires theneglect of the crucial historical definers of the Trinity doctrine(sec. 13).

Analytic theologians have expended much effort on metaphysical modelswhichif accurate would arguably show that “thedoctrine of the Trinity” is coherent (i.e. seemingly notself-contradictory). But only a recent monograph by VlastimilVohánka (2014) asks in depth how, if at all, a person might beable to know that the doctrine of the Trinity is logically possible.Vohánka argues for “Weak Modal Scepticism about theTrinity Doctrine” (83), which is the claim that “it ispsychologically impossible to see evidently and apart from religiousexperience that the Trinity doctrine is logically possible”(86). The arguments for this conclusion defy easy summary (but seeChapter 7 and Jaskolla 2015). What is “the doctrine” inquestion? Vohánka uses a minimal definition, that “thereare three persons, each of whom is God but there is just one beingwhich is God” (47). Admittedly, this better fits one-selftheories than it does three or four-self theories (52–57) Likemost, Vohánka assumes that a Trinity doctrine is essential toChristianity (57–58), so the main thesis implies theimpossibility of knowing that Christianity is logically possible. Butthe overall project is not an attack on the truth or knowability ofChristianity (see the author’s clarifications about his aims on244–47, 276–77). Rather, such claims as the Trinity andChristianity seemingly can’t be evident to us (i.e. roughly,can’t be obviously true to us, as is 1+1=2 and suchpropositions–see 18), and moreover, we shouldn’t expectthat we’ll have any religious experience in this life which issufficient to make them evident (277). For all that’s been said,such claims “may well be epistemically justified, well-argued,have clearly high non-logical probability, etc.”. But theChristian philosopher should give up on “fulfilling theclassical idea of evidentness in matters viewed by him as of utmostimportance: the truth of Christianity and of the Trinitydoctrine” (279).

5.4 Competing Narratives

In some scholarly circles it is taken as obvious that New Testamentteaching is not trinitarian–that it neither asserts, norimplies, nor assumes anything about a tripersonal god (see e.g. Baber2019, 148–56; Küng 1995, 95–96; see alsosupplement on the history of Trinity doctrines, section 2). But most analytic literature on the Trinity assumes the truth of anorthodox narrative about where Trinity theories come from. Accordingto this, from the beginning Christians were implicitly trinitarian;that is, they held views which imply that God is a Trinity, buttypically did not realize this or have adequate language to expressit. By at least the late 300s, they had gained enough new languageand/or concepts to express what they had been committed to allalong.

But in recent analytic literature on the Trinity there are twocounternarratives, both of which see the idea of a triune God asentering into Christian traditions in the last half of the 300s. BeauBranson (2022) argues that “Monarchical Trinitarianism”,which in his view correctly understands the theology of theauthoritative fourth century Greek “fathers” (Basil ofCaesarea, Gregory of Nyssa, and Gregory of Nazianzus) is a trinitariantheology on which “Strictly speaking, when used as a singularterm, the name ‘God’ refers to the Father” (22). Hecontrasts this with most other Trinity theories, which he calls“egalitarian” or “symmetrical”, theories onwhich “all three persons have an ‘equal claim’ tobeing called ‘God,’in any and every sense”(24). Branson criticizes Tuggy’s (2016a) analyses of theconceptstrinitarian andunitarian and offers rivaldefinitions on which “Monarchical Trinitarianism” countsas trinitarian and not unitarian. To be trinitarian, a theology needsonly to assert that “there are exactly three divine‘persons’ (or individuals, etc.).Nevertheless…there is exactly one God” (2022, 17). AsBranson understands the history of Christian theology, the idea that“the Trinity” is a tripersonal God is a misunderstandingof tradition which is due particularly to “Western”thinkers, such as Augustine. Branson cites some recent Orthodoxtheologians who hold, like John Behr, that “there is not One Godthe Trinity, but One God Father Almighty” (Behr 2018, 330). Inreply, Tuggy (2020) has argued that recent Orthodox theologians seemdivided on this point, and that the idea of a triune God (the one Godas the Trinity) is found even in some of the Greek writers Bransonclaims as exemplars of theological orthodoxy.

Another recent counternarrative sees ancient mainstream Christiantheology as changing from unitarian to trinitarian. Tuggy (2019,2024a) argues that in the New Testament the one God is not the Trinitybut rather the Father alone. The argument moves from facts mostlyabout the texts of the New Testament to what the authors probablythought about the one God, using what philosophers of science call thelikelihood principle or the prime principle of confirmation. Tuggysees such identification of the one God with the Father dominatingearly Christian theologies until around the time of the secondecumenical council in 381 C.E. (see the supplementary documentsonunitarianism and on thehistory of views on the Trinity). Then, the Son and the Spirit, which in many 2nd to early 4th centurytheologies were two lesser deities in addition to God, were taught to,together with the Father, somehow comprise the one God, the Trinity(2016b, secs. 2–3).

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