Divine illumination is the oldest and most influential alternative tonaturalism in the areas of mind and knowledge. The doctrine holds thathuman beings require a special divine assistance in their ordinarycognitive activities. Although most closely associated with Augustineand his scholastic followers, the doctrine has its origins in theancient period and would reappear, transformed, in the early modernera.

• 1. Orientation
• 2. The Ancient Background
• 3. Augustine
• 4. Thirteenth-century Franciscans
• 5. Thomas Aquinas
• 6. Henry of Ghent
• 7. John Duns Scotus
• 8. Epilogue
• Bibliography
  • Primary Literature
  • Secondary Literature
• Academic Tools
• Other Internet Resources
• Related Entries

1. Orientation

The theory of divine illumination is generally conceived of asdistinctively Christian, distinctively medieval, and distinctivelyAugustinian. There is some justification for this, of course, inasmuchas Christian medieval philosophers gave the theory serious andsustained discussion, and inasmuch as Augustine gave illumination avery prominent role in his theory of knowledge. Still, it is better tothink of the theory in a wider context. Divine illumination played aprominent part in ancient Greek philosophy, in the later Greekcommentary tradition, in neo-Platonism, and in medieval Islamicphilosophy. Moreover, it was Christian medieval philosophers, near theend of the thirteenth century, who were ultimately responsible fordecisively refuting the theory. I will suggest that we view this lastdevelopment as the first great turning point in the history ofcognitive theory.

I understand a theory of divine illumination to be a theory on whichthe human mind regularly relies on some kind of special supernaturalassistance in order to complete (some part of) its ordinary cognitiveactivity. The assistance must besupernatural, of course, orit will not count asdivine illumination. It must bespecial, in the sense that it must be something more than thedivine creation and ongoing conservation of the human mind. (If thisby itself were to count as illumination, then all theists would becommitted to the theory of divine illumination.) The mind mustregularly rely on this assistance, in order to complete itsordinary cognitive activity: otherwise, an occasionalmystical experience might suffice to confirm a theory of divineillumination. But a defender of the theory need hold only that werequire this assistance forsome part of our ordinarycognitive activities: hardly anyone has supposed that every form ofhuman cognition requires divine illumination.

It is useful to think of divine illumination as analogous to grace.Just as a proponent of grace postulates a special divine role on thevolitional side, so a proponent of divine illumination postulates aspecial divine role on the cognitive side. Grace is intended as anexplanation not of all human desires and motivations, nor even of allvirtuous desires and motivations. Rather, the proponent of grace holdsthat there is a certain class of volitional states, crucial to humanwell-being, that we can achieve only with special divine assistance.Likewise, the theory of divine illumination is intended as anexplanation not of all belief, nor even of all knowledge. Rather, thetheory holds that there are certain kinds of knowledge, crucial tocognitive development, that we can achieve only with special divineassistance. It is an odd fact that, despite the close analogy, graceis regarded not as a philosophical question, but as a theological one.It is an equally odd fact that, whereas divine illuminationhasn’t generally been regarded as plausible since the thirteenthcentury, grace continues to be taken seriously by many theologians.Perhaps both of these facts can be accounted for by motivationalpsychology’s relative obscurity in comparison to cognitivepsychology.

For most people today it is hard to take divine illuminationseriously, hard to view it as anything other than a quaint relic. Afirst step toward developing a proper perspective on the theory is tosee it in its broader context, not as peculiarly Christian ormedieval, but as an assumption shared by most premodern philosophers.A second step in the same direction is to identify and to takeseriously the philosophical problem that drives illumination theory.In large part, the theory has been invoked to explain rational insight— that is, a priori knowledge. For much of the modern era,philosophers have been preoccupied with empirical knowledge and havenot had much interest in this topic. (Recently, this situation haschanged notably; for foundational recent treatments, see Bealer 2000and Bonjour 1998.) To see how something like divine illumination couldhave ever seemed at all plausible, one has to see how deeply puzzlingthe phenomenon of rational insight actually is. One way of seeingthis, and of seeing how little we understand rational insight, is tolook at cases where something goes wrong. A recent biography of theNobel-prize winning mathematician John Nash describes his long periodof mental illness, during which time he held various odd beliefs suchas that extraterrestrials were recruiting him to save the world. Howcould he believe this, a friend asked during a hospital visit, givenhis devotion to reason and logic?

“Because,” Nash said slowly in his soft, reasonablesouthern drawl, as if talking to himself, “the ideas I had aboutsupernatural beings came to me the same way that my mathematical ideasdid. So I took them seriously” (Nasar 1998, p.11).

In a case such as this we don’t know what to do, because we areaccustomed to give unhesitating trust to the deliverances of purereason. But why should we trust reason in this way? Why should we haveconfidence that others can come to share our insights? Where does itcome from? The theory of divine illumination attempts to answer suchquestions.

2. The Ancient Background

What follows is by no means a comprehensive survey. Still, it seemsuseful to begin near the beginning, with this remark by Socrates fromtheApology:

I have a divine or spiritual sign which Meletus has ridiculed in hisdeposition. This began when I was a child. It is a voice, and wheneverit speaks it turns me away from something I am about to do, but itnever encourages me to do anything (31d, tr. Grube).

This appears to be an entirely straightforward expression of a theoryof divine illumination. It is not clear who is providing theillumination. Apuleius (fl. 150 CE) would later identify the source asa certain kind of friendly demon, and argue that it was only fittingfor Socrates, the most perfect of all human beings, to receive suchillumination (De deo Socratis, XVII–XIX). (This ideathat illumination comes to those who deserve it would be proposed byAugustine as well [e.g.,De magistro 11.38], but abandoned inhis later writings as untenable.) As one might expect from Socrates,his illumination seems restricted to the moral sphere. Its form isunclear: is it propositional? (seePhaedrus 242bc) Is itmerely the pang of conscience? (For discussion of these and otherquestions, see e.g. the papers collected in Destrée and Smith2005.) Whatever the details, Socrates is explicitly describing a kindof cognitive guidance that has a “divine or spiritual”source. The passage may be an embarrassment to classicists, but itsurely belongs in the same tradition as later medieval endorsements ofillumination.

Not all appeals to the divine involve this sort of directcommunication. (Indeed, Socrates’s reference to a“voice” is quite extraordinary.) But the leading figuresin ancient Greek philosophy were equally committed to some kind ofdivine role in cognition. Plato’s theory of recollectionpresupposes that the human mind somehow has built into it a grasp ofthe Forms, suggesting that at some point the soul must have receivedsome kind of illumination. Indeed, Plato’s arguments forrecollection anticipate the two lines along which medieval views wouldlater develop. TheMeno focuses on a priori, rationalinsight, as illustrated by the slave’s ability to see forhimself the validity of a geometrical proof. ThePhaedo incontrast focuses on universal properties — Equality, forinstance, as compared with two equal sticks (74a) — contrastingthe changeable imperfection of the physical world with the exemplaryperfection of the Forms. Medieval philosophers from Augustine on,although largely lacking in firsthand knowledge of Plato, would arguefor illumination along both of these lines.

Aristotle too seems to invoke the divine. He describes the activeintellect in this way:

This intellect is separate, unaffected, and unmixed, being in essenceactivity…. It is not the case that it sometimes thinks and atother times not. In separation it is just what it is, and this aloneis immortal and eternal (De anima III 5, 430a17–23).

There is of course unending controversy over the meaning of this text.One very common reading, in ancient times and our own, is that thisactive intellect is something divine, not a human faculty at all. Ifone then makes the further, natural assumption that the activeintellect participates in ordinary human cognition, then Aristotlewould clearly be committed to a version of divine illumination. (Oneshould, however, be cautious in supposing that Aristotle’snous poietikos plays anything like the role played by thescholasticintellectus agens. See Haldane 1992.) Not everyonehas been persuaded that this active intellect is something literallyseparate and divine. But even if one supposes that the activeintellect is a part of the human soul, it is nevertheless difficult toavoid the suspicion that some sort of special divine influence is atwork. Everything in the passage cries out for some sort ofsupernatural element in human cognition.

Alexander of Aphrodisias (fl. 200 CE) was influential in pushing theseparate-and-divine reading ofDe anima III.5, and Islamicphilosophers (most notably Ibn Sīnā [980–1037] and IbnRushd [c.1126–c.1198]) would later follow suit. Themistius (4thcentury CE), in contrast, championed the part-of-soul reading, andThomas Aquinas (1225–1274) would second this interpretation. Afull treatment of this topic would cover the later Aristotelian andPlatonic traditions, Greek and Islamic. But here I will focusexclusively on the Latin West, where it was Augustine who played thedecisive role in formulating the doctrine of illumination. (For auseful survey of ancient and medieval Aristotelian accounts of agentintellect, see Brentano 1992. On the later Platonic tradition, seeGersh 1978. The Islamic tradition deserves a full essay in its ownright, covering not just names well known in the Latin West, but alsofigures like Suhrawardi and Mulla Sadra, central figures in theIslamic illuminationist tradition [see Walbridge 2005].)

3. Augustine

Throughout his long literary career, Augustine (354–430)stresses the role of divine illumination in human thought. One couldchoose almost any work to illustrate this point; here I will focus onthe most familiar of all, theConfessions, where Augustineinvokes divine illumination constantly, and makes bold claims for itsglobal necessity:

The mind needs to be enlightened by light from outside itself, so thatit can participate in truth, because it is not itself the nature oftruth. You will light my lamp, Lord (IV.xv.25).

None other than you is teacher of the truth, wherever and fromwhatever source it is manifest (V.vi.10).

You hear nothing true from me which you have not first told me(X.ii.2).

Truth, when did you ever fail to walk with me, teaching me what toavoid and what to seek…. Without you I could discern none ofthese things (X.xl.65).

Even during the Middle Ages, Augustine’s readers disagreed onthe precise nature of his theory. One thing that seems clear fromthese passages alone is that divine illumination is an influence thatwe receive in an ongoing way throughout our lives. Thomas Aquinaswould later understand illumination as an infusion all at once at thestart (see below), but this seems untenable as an interpretation ofAugustine. The mind needs to be enlightened “from outsideitself”; “it is not itself the nature of truth”;“youwill light my lamp, Lord” (he has not doneso already); truth “walk[s] with me,” rather than merelysetting me in motion at the start.

To speak of this influence as an illumination is of course to use ametaphor, one not likely to be unpacked fully. Our own minds presentenough of a puzzle to us: when we try to understand how the divinemind might influence our own, we must inevitably fall back onmetaphor. Still, there are a variety of ways in which we might seeksome clarification. In particular, it is helpful to distinguish twoways in which God might provide illumination. First, he might simplygive us information of certain kinds, telling us how things are. Thisis how illumination is most often understood, at least implicitly. Buta second possibility is that God would provide not the informationitself, but the insight into the truth of the information. On thissecond model, we would frame beliefs on our own, and God wouldilluminate our minds so that we could see the truth. In other words,God would supply the justification. It is clear that sometimesillumination takes the first form: much of Biblical revelation just isillumination in this sense. But Augustine’s theory ofillumination seems largely to be of the second kind. Consider thisfamous passage from theConfessions:

If we both see that what you say is true, and we both see that what Isay is true, then where do we see that? Not I in you, nor you in me,but both of us in that unalterable truth that is above our minds(XII.xxv.35).

At issue here is biblical interpretation. When a reading is advancedthat seems clearly correct, how is it that everyone listening graspsthe truth of that reading? It is not that God gives us theinterpretation itself, but that he allows us to see that theinterpretation is true.

This understanding of illumination is particularly apparent in theDe magistro, where Augustine argues that only God can teachus. Of course, other people can tell us things, and can therebycommunicate ideas to us. And we can believe what others tell us:indeed, our lives would be impoverished if we didn’t regularlyaccept what others tell us. But all of this stays at the level of merebelief. It is not knowledge unless we grasp with our minds the truthof what we are hearing:

When I speak the truth, I do not teach someone who sees these truths.For he is taught not by my words but by the things themselves mademanifest within when God discloses them (12.40).

The speaker’s role is not irrelevant in this process. My wordsgive listeners an idea that they can then verify for themselves inlight of God’s illumination. Illumination is what allows us togo from mere true belief to knowledge. Illumination providesjustification.

This account is most attractive in cases of a priori knowledge or purereasoning, where we grasp through the mind alone that an argument isvalid or that a conclusion is necessary. But there is another strainof thought running through Augustine, one that focuses on themind’s ability to transcend the untrustworthy senses and graspthe truth that lies beyond mere appearances. The following passage isvery often cited in this connection:

Everything that the bodily senses attain, that which is also calledsensible, is incessantly changing…. But what is not constantcannot be perceived; for that is perceived that is comprehended inknowledge. But something that is incessantly changing cannot becomprehended. Therefore we should not expect pure truth from thebodily senses (Eighty-three Different Questions, q.9).

In one stroke, this argument rules out the physical world as an objectof pure truth, and rules out the senses as a source for that truth. Itmust be the mind, then, with which we attain truth, and that truthmust be something beyond the sensible world. Plainly, the mind cannotrely on the senses. But what else is there? The conclusion we areinvited to reach is that the mind must rely on God.

One might try assimilating this line of thought to those passageswhere Augustine has in mind necessary a priori truths. But it is morenatural to take this in a different way, as an account of how the mindgoes beyond the sensible data to a grasp of the real essences ofthings. Accordingly, the theory of divine illumination would be put totwo very different sorts of work in the later Middle Ages: as anaccount of a priori knowledge, and as an account of concept formation.Each account raises its own set of issues. Taken in the first way,divine illumination has to compete against the claim that the mind isnaturally capable of grasping such truth. Taken in the second way,questions immediately arise about the nature of conceptual knowledge.Do essences (or properties in general) exist in the physical world? Dothey exist only in the divine mind? Do the senses play any role in theprocess of concept formation? Later medieval philosophers would handlethese issues in interestingly different ways.

4. Thirteenth-century Franciscans

Augustine’s position would remain ascendant among Christianphilosophers for most of the Middle Ages. Thirteenth-centuryFranciscans, led by figures such as Bonaventure (c.1217–1274)and Matthew of Aquasparta (c.1237–1302), gave the theory adetailed and systematic defense, focusing on the changeability andhence uncertainty of the human mind and the sensory world (see Marrone2001). Bonaventure characteristically argues,

Things have existence in the mind, in their own nature (propriogenere), and in the eternal art. So the truth of things as theyare in the mind or in their own nature — given that both arechangeable — is sufficient for the soul to have certainknowledge only if the soul somehow reaches things as they are in theeternal art (De scientia Christi, q.4 resp.).

Certain knowledge requires steadfast unchangeability. Since that canbe found only in the divine mind, and since we have access to thedivine mind only through illumination, certain knowledge requiresillumination. (On the early thirteenth century see Faucher 2019; onBonaventure see Solignac 2022.)

This line of argument came to seem increasingly old-fashioned as thethirteenth century progressed. The growing influence ofAristotle’s theory of cognition, as developed in particular bythe Dominican friars Albert the Great (c.1200–1280) and hisstudent, Thomas Aquinas (c.1225–1274), offered an impressivepicture of how human beings might be able to achieve certain knowledgedespite the changeability of mind and matter. These developmentsstruck many Franciscans as a betrayal of Christianity. John Pecham(c.1225–1292), in a letter dating from 1285, writes

I do not in any way disapprove of philosophical studies, insofar asthey serve theological mysteries, but I do disapprove of irreverentinnovations in language, introduced within the last twenty years intothe depths of theology against philosophical truth and to thedetriment of the Fathers, whose positions are disdained and openlyheld in contempt.

Continuing, Pecham criticizes the doctrine

which fills the entire world with wordy quarrels, weakening anddestroying with all its strength what Augustine teaches concerning theeternal rules and the unchangeable light…. (quoted in Gilson1955, p.359).

At roughly the same time, Roger Marston (c.1235–1303) writes ofthose who, “drunk on the nectar of philosophy … twistedtoward their own sense all of Augustine’s authoritative texts onthe unchanging light and the eternal rules” (Quaestionesdisputatae de anima 3 ad 30).

Marston’s view is particularly interesting because he proposes asynthesis of Augustine and Aristotle. On his view,

It is necessary to posit in our mind, beyond the phantasms orabstracted species, something by which we to some degree attain theunchanging truths. I believe this to be no different than theinfluence of the eternal light…. For the eternal light,irradiating the human mind, makes a certain active impression on it,from which a certain passive impression is left in it, which is theformal principle of cognizing the unchanging truths (De anima3, p.263).

Rather than dismiss the agent intellect as superfluous, Marstonfollows Alexander of Aphrodisias et al. in treating the agentintellect as separate and divine — indeed, as God himself.Earlier in the thirteenth century, William of Auvergne(c.1180–1249) had in effect identified the agent intellect withGod (The Soul 7.6; cf. Gilson 1926–27, pp.67–72).Such cases illustrate how the various medieval disputes over whetherhuman beings might share a single intellect — so absurd on theirface — are in fact simply alternative formulations of thedispute over divine illumination. But there were subtle differencesamong the various approaches. So whereas Auvergne largely turns hisback on Aristotle, Marston is more accommodating. In addition to thedivine agent intellect, he allows that each human being possesses itsown agent intellect.

On Marston’s account, Aristotle and Augustine turn out to beentirely in harmony: each uses his own terminology to defend the sametheory of divine illumination (De anima 3, p. 258).Étienne Gilson (1933) has characterized Marston’sposition as an Avicennized Augustinianism (Augustinismeavicennisant). But this label prejudices the case in favor ofAquinas’s perspective: it assumes that Marston has been seducedby an Islamic misreading of Aristotle, and it closes off thepossibility that Augustine and Aristotle might have more in commonthan is typically allowed.

The case of Peter John Olivi (1247/8–1298) demonstrates howprecarious a position the illumination theory held by the 1280s.Olivi, a Franciscan whose work would eventually be condemned by hisown order, presents a compelling critique of the Augustinianillumination theory (I Sent., q. 2), presenting his commentsin the form of “cautions” (cavenda). The theory,he notes, is often very vague with respect to the actual process ofillumination. And in running through the various possible accounts ofthe process available to a defender of the theory, Olivi appears torule out every one. The eternal reasons cannot represent thingsdistinctly and specifically, because then we would have no need of anysensory input. But if the eternal reasons give us information only ofa general and indistinct sort, then at what level of generality? Doesit supply us with information about species, or genera? If divineillumination is efficacious at any level, why do we seem to need thesenses for all of our concepts? Olivi’s questions and cautionsgo on and on. But after laying an entire minefield of this sort foranyone who would defend divine illumination — at ad 6 he rejectsthe Augustinian argument set out above by Bonaventure — henevertheless comes to the surprising conclusion that he accepts thetheory:

These things, since I don’t know how to analyze them fully, Iset out only as cautions. For although the stated position is initself venerable (sollemnis) and sensible, it couldnevertheless be quite dangerous to those who are not carefullysupervised. And so I hold the stated position as it is, because itbelongs to men who are highly venerable. Nevertheless I leave anexposition of the above to their wisdom (q. 2, pp. 512–13).

This was a favorite strategy of Olivi’s: to criticize a theoryfiercely, exposing seemingly devastating difficulties, and then toembrace the theory anyway, as a pious gesture of respect. It’shard to resist reading between the lines, and concluding that dusk wasfast approaching for the theory of divine illumination.

5. Thomas Aquinas

Thomas Aquinas is often thought of as the figure most responsible forputting an end to the theory of divine illumination. Although there issome truth to this view, as we will see, it seems more accurate toregard Aquinas as one of the last defenders of the theory, as aproponent of innate Aristotelian illumination.

A vivid example of the way Aquinas moves from an Augustinian to anAristotelian framework occurs in his Treatise on Human Nature(Summa theologiae 1a 75–89), where he considers theAugustinian claim that “pure truth should not be looked for fromthe senses of the body” (84.6 obj. 1). In reply, Aquinas invokesthe Aristotelian agent intellect:

From those words of Augustine we are given to understand that truth isnotentirely to be looked for from the senses. For we requirethe light of agent intellect, through which we unchangeably cognizethe truth in changeable things, and we distinguish the thingsthemselves from the likenesses of things (ad 1).

It is not at all clear, here or elsewhere, how the agent intellectcarries out the two tasks he describes. (If Aquinas had given us asatisfactory account of this, he would have thereby solved two of theleading problems of epistemology.) But for present purposes it isenough to notice how Aquinas seems to replace Augustinian illuminationwith the Aristotelian agent intellect. Thus the traditional verdicthas been that Aquinas replaced Augustine with Aristotle, and exchangedillumination for abstraction.

There is more to the story. In the immediately preceding article,Aquinas explicitly discusses Augustinian divine illumination, andreaches the affirmative conclusion that “the intellective souldoes cognize all true things in the eternal reasons” (84.5sc).Often this affirmative conclusion gets treated as little more than lipservice to the authority of Augustine, and the article as a whole getstaken as a backhanded repudiation of illumination theory: affirmingthe theory in form but denying it in substance. This is a misreading.Aquinas sees something important in Augustine’s theory,something worth preserving.

Aquinas does reject certain conceptions of divine illumination. Hedenies that human beings in this life have the divine ideas as anobject of cognition. And he denies that divine illuminationis sufficient on its own, without the senses. Neither of these claimswas controversial. What Aquinas further denies, and what wascontroversial, was the claim that there is a special ongoing divineinfluence, constantly required for the intellect’s operation.Aquinas instead argues that human beings possess a sufficient capacityfor thought on their own, without the need for any “newillumination added onto their natural illumination” (Summatheol. 1a2ae 109.1c). From one perspective this makes for animportant difference between Aquinas and his Franciscancontemporaries. But from another perspective the difference seemsslight, because Aquinas is by no means removing God from the picture.Here is how he expresses his endorsement of illumination theory:

It is necessary to say that the human soul cognizes all things in theeternal reasons, through participating in which we cognize all things.For the intellectual light that is in us is nothing other than acertain likeness of the uncreated light, obtained throughparticipation, in which the eternal reasons are contained. Thus it issaid in Psalm 4,Many say, Who shows us good things? To thisquestion the Psalmist replies, sayingThe light of your face,Lord, is imprinted upon us. This is as if to say, through thatseal of the divine light on us, all things are shown to us (Summatheol. 1a 84.5c).

There is some temptation to take all of this simply as an expressionof Aquinas’s more general view that God is the first cause ofall things. He writes, for instance,

All active created powers operate in virtue of being directedand moved by the Creator. So it is, then, that in all cognition of thetruth, the human mind needs the divine operation. But in the case ofthings cognized naturally it does not need any new light, but onlydivine movement and direction (In de trinitate pro. 1.1c).

Here there seems to be nothing special about the intellect’sneed for illumination. The intellect, like all of nature, needs God asits first mover. If you like, think of this as divine illumination.But viewed under this aspect, it is no wonder the theory wascontroversial. While his Franciscan contemporaries were insisting on aspecial role for God in human cognition, Aquinas seems to move as farin the opposite direction as his theism would permit.

But passages of this last kind are misleading, because Aquinas doessee something especially mysterious about human cognition, and heappeals to God as a way of solving this mystery. The agent intellect,on Aquinas’s view, accounts for our capacity to graspself-evident truths. We have an immediate and direct grasp of thetruth of first principles, such as the principle of noncontradiction(see, e.g.,Summa contra Gentiles II.83.1678). We do notinfer the truth of this principle, we do not discover that it is truethrough any kind of induction. Instead we simply see its truth, assoon as we are confronted with an instance where it applies. This isnot innate knowledge; we are not born knowing these principles. Whatwe are born with is the capacity to recognize their truth as soon aswe are confronted with instances of them. These first naturalconceptions are “the seeds of all the things that aresubsequently cognized” (De veritate 11.1 ad 5). In thissense, Aquinas is even willing to speak of the soul’s having aprior knowledge of everything that it knows:

The soul forms in itself likenesses of things inasmuch as, through thelight of agent intellect, forms abstracted from sensible objects aremade actually intelligible, so as to be received in the possibleintellect.And so, in a way, all knowledge is imparted to us atthe start, in the light of agent intellect, mediated by theuniversal concepts that are cognized at once by the light of agentintellect. Through these concepts, as through universal principles, wemake judgments about other things, and in these universal concepts wehave a prior cognition of those others. In this connection there istruth in the view that the things we learn, we already had knowledgeof (De veritate 10.6c).

Because all of what we know can be traced back to these fundamentalprinciples, there is a sense in which everything we learn, we alreadyknew. An innate grasp of certain basic truths, recognized by the lightof agent intellect, plays a crucial, foundational role.

The light of agent intellect is of course given to us from God —“a certain likeness of the uncreated light, obtained throughparticipation” (1a 84.5c). Without appealing to God, Aquinassees no way of explaining how we recognize the truth of firstprinciples. Neither deductive nor inductive reasoning can account forthe way in which we immediatelysee that such principles aretrue. This insight, then, is simply something we are given:

The light of this kind of reason, by which principles of this kind areknown to us, is imparted to us from God. It is like a likeness of theuncreated truth reflecting in us. So, since no human teaching can beeffective except in virtue of that light, it is clear that it is Godalone who internally and principally teaches us (De veritate11.1c).

The light of agent intellect, a likeness of the divine ideas, is theessential starting point for all knowledge.

Aquinas agrees with his Franciscan contemporaries that intellectivecognition is incomplete without some sort of supernaturally infusedinsight. The only difference is that Aquinas wants that insight to begiven all at once, from the start — bottled up within agentintellect, as we might think of it. His opponents, in contrast, thinkof illumination as an ongoing process, as necessary as the air webreathe. It is easy to see how, at the time, this difference mighthave seemed important. But from our present perspective thedifferences seem rather slight: they seem to be arguing simply overthe means of transmission. Aquinas conceives of illumination as a deepwell within us, whereas the Franciscans conceived of it as rainingdown in drops. (This is a summary of the account in Pasnau 2002,Chapter 10.)

6. Henry of Ghent

Although in a sense Thomas Aquinas defends a version of divineillumination, he in another sense clearly weakens the theory by givingit the status of an innate gift rather than ongoing patronage. Inmaking for the agent intellect a central place in his theory ofcognition, Aquinas has less room for illumination. As the thirteenthcentury progressed, philosophers and theologians were increasinglywilling to make this tradeoff. While the Aristotelian theory ofcognition waxed, the Augustinian theory of divine illumination waned.To combine the two seemed, in the words of Étienne Gilson(1930), “unproductive and even, in a sense,contradictory.”

It is this seemingly contradictory task that Henry of Ghent(c.1217–1293) took upon himself in the years immediately afterAquinas’s death. When Peter John Olivi remarked that he wouldaccept the theory of illumination because it “belongs to men whoare highly venerable” (sec. 4 above), he would have had in mindamong others Henry of Ghent, who would indeed become known as the“Venerable Doctor” (Doctor solemnis). Ghent wasneither Dominican nor Franciscan, but a so-called“secular” master at the University of Paris. His projectwas to defend an Aristotelian theory of cognition while at the sametime reviving divine illumination in its traditional Augustinian form.To those, like Aquinas, who were arguing for the self-sufficiency ofthe human cognitive powers, Ghent replies,

this is true for natural things, as regards knowing what is true ofthe thing…. Pure truth, however, or any truth that must becognized supernaturally, or perhaps any truth at all, cannot be knownwithout God himself doing the teaching (Summa 1.7 ad 1).

On Ghent’s terminology, to know what istrue of a thingis simply to have a veridical impression of it: to represent a thingas it is. To grasp thetruth of a thing, in contrast, is tograsp its nature. Only this latter sort of cognition counts asknowledge in the strict sense, because only here are we getting at theunchanging reality of the material world.

For there is no knowledge of things insofar as they are external ineffect, but insofar as their nature and quiddity is grasped by themind (Summa 2.2 ad 1).

For knowledge of this kind, divine illumination is necessary.

Ghent’s argument is interestingly different from that ofAugustine and his Franciscan followers. Whereas they had dismissed thephysical world as too changeable to be a fit subject for humanknowledge, Ghent believes that pure truth and certain knowledge can behad of the physical world, provided we manage to grasp the realessences of things. Since we cannot do so on our own, we need divineillumination to go beyond sensory appearances, to have genuine insightinto the nature of reality. At its most basic level, Ghent is offeringa critique of the agent intellect. Although he accepts the doctrine ofagent intellect, he refuses to give that faculty the kind of efficacythat it has for Aquinas and other medieval Aristotelians. Notsurprisingly, Ghent proposes reviving the earlier thirteenth-centurytradition of referring to God himself as a kind of agent intellect(Quodlibet 9.15). The way Ghent would synthesize Augustineand Aristotle, in this area, is by identifying those aspects ofAristotle that are incomplete and supplementing them with thenecessary Augustinian illumination. (This is a summary of the accountin Pasnau 1995. All of Henry’s important initial article fromhisSumma on the possibility of knowledge is now available ina translation from Roland Teske.)

7. John Duns Scotus

It was the Franciscan John Duns Scotus, more than anyone else, who putan end to the theory of divine illumination. As Steven Marrone (2001)has shown in detail, there were various authors at the end of thethirteenth century who were ready to reject illumination. Indeed,Ghent himself gave illumination less and less attention in his lateryears. Still, it was Scotus who provided the most impressive andextensive philosophical alternative to illumination theory. (As JohnBoler remarked in correspondence, “as with Nixon’s trip toChina, it probably could only be done by a Franciscan.” On thestory from Bonaventure through Scotus see Adams 2022.) Scotuscriticizes Ghent’s argument in detail (OrdinatioI.3.1.4), arguing against Ghent’s own arguments, against theskeptical consequences that would allegedly come from giving up divineillumination, and against the viability of such illumination in itsown right. With respect to the last point, Scotus argues that if humancognition were fallible in the way Ghent argues, then outsideillumination could not, even in principle, ensure “certain andpure knowledge.” On Ghent’s account, the human mindcooperates with the divine light in achieving such knowledge. Scotusreplies:

When one of those that come together is incompatible with certainty,then certainty cannot be achieved. For just as from one premise thatis necessary and one that is contingent nothing follows but acontingent conclusion, so from something certain and somethinguncertain, coming together in some cognition, no cognition that iscertain follows (Ordinatio I.3.1.4 n. 221).

If one part of a system is fallible, then that fallibility infects theprocess of a whole. Scotus’s startling claim is that if thehuman mind were intrinsically incapable of achieving certainknowledge, then not even divine illumination could save it.

Scotus’s own view is that the human mind is capable of suchknowledge on its own. If by “certain and pure truth” Ghentmeans “infallible truth, without doubt and deception,”then Scotus thinks he has established that human beings “canachieve this, by purely natural means” (Ord. I.3.1.4 n.258). Howcan such a thing be established? How can theskeptic be refuted, without appealing to divine illumination? Scotusdistinguishes four kinds of knowledge:

• self-evident (principia per se nota)
• inductive (cognita per experientiam)
• introspective (cognoscibilia de actibus nostris)
• sensory (ea quae subsunt actibus sensus)

The general strategy is to show that sensory knowledge rests oninductive knowledge, that inductive knowledge rests on self-evidentknowledge, and that introspective knowledge can be defended asanalogous to self-evident knowledge. Scotus’s implicit aim is toshift as much weight as possible onto the broad shoulders ofself-evident knowledge.

For Scotus, the self-evident is the bedrock on which other sorts ofknowledge rest, and so he does not attempt to locate some further setof even more basic truths. Instead, he argues that our self-evidentknowledge is foolproof because of certain psychological facts. Whenone considers a proposition likeEvery whole is greater than itspart, one immediately grasps that the terms are related in such away that the proposition must be true:

There can be in the intellect no apprehension of the terms orcomposition of those terms without the conformity of that compositionto the terms emerging (quin stet conformitas), just as twowhite things cannot arise without their likeness emerging(Ord. I.3.1.4 n. 230).

When we see two white objects we immediately grasp, “withoutdoubt and deception,” their similarity to one another. Likewise,when we grasp a self-evident truth in our mind, we immediately graspits truth. Of course, we won’t grasp the truth of theproposition if we don’t understand the meaning of the terms, butin that case we won’t have truly formed the proposition in ourmind. And in contrast to the analogous case of recognizing similarity,there is no room for sensory error here. The senses help us acquirecertain concepts, but once we have those concepts, the senses drop outof the picture — sensory reliability becomes irrelevant. Scotusoffers the example of a blind man miraculously shown in his dreams animage of black and white. Once he acquires these concepts, he canrecognize as truly and infallibly as anyone — his blindnessnotwithstanding — that white is not black (Ord. I.3.1.4n. 234).

Scotus is unwilling to discard Augustinian illumination entirely, andso he articulates four senses in which the human intellect seesinfallible truths in the divine light. In each sense, the divine lightacts not on us but on the objects of our understanding. By givingobjects their intelligibility (esse intelligibile), thedivine intellect “is that in virtue of which secondarily theobjects produced move the intellect in actuality” (Ord.I.3.1.4 n. 267). When the human mind grasps a self-evident truth, itdoes so immediately and infallibly not because the mind has receivedany special illumination, but because the terms of the proposition arethemselves intelligible: our grasp of a proposition “seems tofollow necessarily from the character of the terms, which characterthey derive from the divine intellect’s causing those terms tohave intelligible being naturally” (Ord. I.3.1.4 n.268). It is not that we are illuminated by the divine light, but thatthe truth we grasp is illuminated.

This marks a turning point in the history of philosophy, the firstgreat victory for naturalism as a research strategy in cognitivetheory. On Scotus’s account, when we grasp some conceptualtruth, nothing miraculous or divine happens within us: “theterms, once apprehended and put together, are naturally suited(sunt nati naturaliter) to cause an awareness of thecomposition’s conformity with its terms” (Ord.I.3.1.4 n. 269). It is of course God that gives the world itsintelligibility, just as it is God that creates our cognitive powers.But what is new in Scotus is the idea that the mind is not a specialcase. From this point forward, divine illumination would rarely beregarded as a serious philosophical possibility.

8. Epilogue

It is easy to miss the significance of what Scotus brought about: inpart because it now seems so inevitable, in part because Scotus comesat the end of a gradual trend toward naturalism, and in part becauseuntil only recently it was generally supposed that nothing of muchphilosophical importance happened between Aristotle and Descartes. Yetif one looks at the big picture of our evolvingphilosophical/scientific understanding of the mind, then it is clearthat something important happened at the end of the thirteenthcentury.

Still, Scotus’s impact should not be overstated. Although divineillumination, so called, would no longer have many prominentsupporters, the tendency toward supernatural explanations of cognitivephenomena would survive well beyond the Renaissance. Descartes, totake one prominent example, can speak of “certain seeds of truthwhich are naturally in our souls” (Discourse on Method6, AT VI:64), and of “ideas implanted in the intellect bynature” (Principles of Philosophy 2.3). In its details,the view is strikingly similar to Aquinas’s: Descartesidentifies these ideas as the basis of our knowledge of firstprinciples; he holds that the ideas themselves are formed only invirtue of sensory impressions; he identifies God as the ultimatesource of these ideas. Moreover, if Descartes is playing Aquinas, inmodern dress, then as Henry of Ghent we can cast Malebranche, whoargues that “All our ideas must be located in the efficacioussubstance of the Divinity, which alone is intelligible or capable ofenlightening us, because it alone can affect intelligences”(Search after Truth, p. 232). Malebranche’s remarkableview — in support of which he quotes Augustine — is thatall our ideas are seen in God. This is illumination theory, all overagain. But by the seventeenth century the philosophical context haschanged so dramatically that these modern developments must beregarded as a different topic.

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Related Entries

Aquinas, Thomas |Arabic and Islamic Philosophy, special topics in: mysticism |Augustine of Hippo |Duns Scotus, John |Mulla Sadra |Olivi, Peter John |Suhrawardi

Acknowledgments

This entry has benefited greatly from suggestions by Marilyn Adams,Jenny Ashworth, John Boler, Peter King, Gyula Klima, Neil Lewis, TimNoone, Sarah Pessin, Christopher Shields, and John Wippel.