Dualism

First published Tue Aug 19, 2003; substantive revision Fri Oct 17, 2025

This entry concerns dualism in the philosophy of mind. The term‘dualism’ has a variety of uses in the history of ideas.In general, dualism is the view that, for some particular domain,there are two fundamental kinds. In theology, for example a‘dualist’ is someone who believes that Good and Evil– or God and the Devil – are independent and more or lessequal forces in the world. In the philosophy of mind, dualism is thetheory that mind and body – or the mental and the physical– are, in some fundamental sense, different kinds of things.Dualism contrasts with monism, which says that there is only onefundamental kind; and, rather less commonly, with pluralism, which isthe view that there are many fundamental kinds. Dualism usually entersphilosophy as a response to the mind-body problem, where its maincompetitor is materialism, the form of monism that says that mind andbody are both ultimately physical. Dualism is very common in thehistory of ideas. Today, dualism is the second most popular responseto the mind-body problem among professional philosophers, aftermaterialism and ahead of idealism and panpsychism.

1. Dualism and the Mind-Body Problem

Humans have, or seem to have, the sort of properties attributed in thephysical sciences. These physical properties include size, weight,shape, colour, and motion through space and time. Humans also have, orseem to have, mental properties, which we do not attribute to typicalphysical objects. These mental properties include perceptualexperience, emotional experience, beliefs, desires, agency, andsubjecthood or selfhood. In its broadest form, the mind-body problemis the problem of explaining how humans and other mentally endowedbeings end up having, or seeming to have, these very differentcharacteristics (Weir 2023, 1–7). In a more specific form, whichtakes centre stage after the emergence of mechanistic science in theseventeenth century, the mind-body problem is the problem ofreconciling the apparent ontological disparity between mind and bodywith the fact that they seem to interact closely (Westphal 2016,1–3, 43).

The problem has a number of components. These include the ontologicalquestion, what are mind and body, and is one ultimately reducible to,or in some other sense ‘nothing over and above’ the other? They alsoinclude the causal question: do physical states influence mentalstates, do mentals states influence physical states, and if so, how?Different aspects of the mind-body problem arise for different aspectsof the mental, such as consciousness, intentionality, agency, personalidentity, and subjecthood.

Dualism is one of three classic responses to the mind-body problemalongside materialism and idealism (Wolff 1751). Materialism says thatthe mind, insofar as it truly exists, is fundamentally physical.Idealism is the converse view that matter, insofar as it truly exists,is fundamentally mental. Dualism is the view that mind and body areboth real and fundamentally distinct. A fourth option which has gainedprominence in recent discussions is a kind of panpsychism according towhich the things described by physical science are deep-down, partlyor wholly, mental in nature (Freeman 2006, Alter and Nagasawa 2015,Goff and Moran 2022). There is some disagreement as to whether thesepanpsychist theories form a subclass of one or more of the threeclassic views, or a distinctive class of their own (Weir 2023,87–91). For an extensive taxonomy of responses to the mind-bodyproblem as it concerns consciousness see Kuhn (2024).

Dualism usually enters philosophical discussions as one possibleresponse to the mind-body problem, especially as it pertains toconsciousness. A 2020 survey suggests that dualism is, in thiscontext, the second most popular response to the mind-body problemamong professional philosophers (Bourget and Chalmers 2023).Twenty-two percent of respondents indicated that they ‘accept orlean towards’ dualism, compared to fifty-one percent formaterialism and eight percent for panpsychism. Idealism was notincluded as a possible response to this question (though seven percentindicated that they accept or lean towards idealism in response to aquestion about external-world scepticism).

More recently, dualism has also been discussed in the context of the‘meta-problem of consciousness’. This is the problem ofexplaining why people report dualist intuitions about consciousness,or why dualism about consciousness seems true, irrespective of whetherit is actually true (Chalmers 2018, Rickabaugh and Moreland 2023,83–86). The meta-problem of consciousness arises because thereis general agreement that dualism is intuitively appealing, even amongits opponents (see Taliaferro 1994, 26 fn. 10). Analogous‘meta-problems’ concerning other aspects of the mind-bodyproblem such as intentionality and personal identity exist but havenot yet received comparable attention. A final area where dualism isfrequently discussed is in the philosophy of religion, where responsesto the mind-body problem intersect with religious views about thesoul.

Other entries which concern aspects of the mind-body problem include(among many others):behaviorism,consciousness,eliminative materialism,epiphenomenalism,functionalism,identity theory,intentionality,mental causation,neutral monism,panpsychism, andphysicalism.

2 History of Dualism

An early form of dualism can be found in the idea that humans possessa psychological core, the self or soul, that survive bodily death.Versions of this idea appear in some of the earliest survivingsources, including Shang Dynasty oracles, theEpic ofGilgamesh, the Homeric poems, the Hebrew Bible and Egyptianfunerary texts. Religious practices involving communication with thespirits of the dead appear to be universal across cultures (Steadmanet al. 1996). Data from infant psychology suggest that dualism of thiskind may be part of how humans naturally conceive of themselves,irrespective of environmental and cultural factors (Wellman 1990, 58;Bering 2006; Bloom 2007; cf. Hodge 2008). Early philosophicaldiscussions of dualism emerge in Vedic India and Classical Greece.Both traditions have a powerful influence on philosophy of mind today.Works from a third major centre of ancient philosophical texts, China,also regularly presuppose dualism (Slingerland 2013). However, earlyChinese philosophy is less preoccupied with the mind-body problem thanthat of India and Greece. Two events have a profound impact onsubsequent discussions of dualism: the spread of the Abrahamicreligions in late antiquity; and the emergence of mechanistic sciencein the early modern period.

2.1 Dualism in Indian Philosophy

A central focus of India’s foundational philosophical texts, theUpanishads (c. 700–500 BCE), is the nature and destinyof the soul (atman). TheUpanishads present thetheory that the soul is an unchanging and imperishable entity thatsurvives bodily death and undergoes successive reincarnations(Olivelle 1998). This view would be taken up by numerous subsequentIndian philosophical traditions. A description of the same idea fromtheBhagavad Gita reads:

There has never been a time when you and I… have not existed,nor will there be a time when we will cease to exist. As the sameperson inhabits the body through childhood, youth, and old age, so tooat the time of death he attains another body. The wise are not deludedby these changes… The body is mortal, but that which dwells inthe body is immortal and immeasurable. (Ch. 2, 12–18)

Two of the six ‘orthodox’ Indian philosophical schools,Samkhya and Vaisheshika, articulate detailed dualist theories whichare further developed by their sister schools, Yoga and Nyaya. Of theremaining two ‘orthodox’ schools, Mimamsa appears topresuppose dualism, while focussing on other matters, and Vedantadevelops both dualist and idealist sub-schools (Radhakrishnan andMoore 1998).

Of the two surviving ‘heterodox’ Indian philosophicalschools—those that do not recognise the authority of Hinduscripture—Jainism advances a distinctive form of dualism, whileBuddhism develops sub-schools with various theories of the mind. Thetexts of a third ‘heterodox’ school, Carvaka, are mainlylost, but fragments and second-hand reports show that it embraced aform of materialism.

Important differences exist between classical Indian forms ofmind-body dualism. For example, Samkhya and Yoga represent the soul(purusha) as pure awareness. Vaisheshika and Nyaya, bycontrast, attribute to the soul (atman) not justconsciousness, but also volition and cognition. All four represent theindividual soul as pervading the cosmos, while Jain texts state thatit (ordinarily) fills only the body that it occupies, like the lightfrom a lamp filling a room.

A distinctive version of mind-body dualism appears in the earlyBuddhist tradition,Abhidharma. TheAbhidharma Pitaka (a collection of works by multipleauthors, existing in several recensions) contends that what we mistakefor the soul or self is really a bundle of fleeting atom-events called‘dharmas’. These dharmas are nonetheless divided into whatappear to be fundamentally mental and fundamentally physical kinds,making this position a form of dualism, albeit one that departsradically from other Indian theories in rejecting the idea of anenduring soul.

The classical Indian dualist theories retain varying degrees ofinfluence into the present day. Buddhism declined in India and inCentral Asia in the Middle Ages, but flourished in East Asia, carryingwith it a philosophical interest in the mind-body problem and thenature and (non-)existence of the soul. One result was an earlyargument for the fundamentality of consciousness advanced by the Tangdynasty Buddhist monk, Guifeng Zongmi (780–841 CE):

Moreover, theqi of Heaven and Earth is fundamentally lackingin awareness. If humans are endowed withqi that lacksawareness, how can awareness suddenly arise? Grass and trees areendowed with the sameqi, so why do they not have awareness.(On Humanity, 100)

An important shift in Indian philosophy occurred in the wake ofShankara’s (c. 8th century CE) exposition of the non-dualist(advaita) sub-school of Vedanta. Gradually, Advaita Vedantagained a prominence unrivalled by other Indian schools (except perhapsYoga). This explains the perception in some sources that Indianphilosophical thought leans towards idealism over dualism.

2.2 Dualism in Greek Philosophy

There exists evidence of both mind-body dualism and the cycle ofreincarnation among the Greek pre-Socratics, especially thePythagoreans. The resemblance between these ideas and those of VedicIndia has led to speculation about the possibility of a common sourceor influence between the two (McEvilly 2002, Ch. 4). Hard evidence forsuch a theory remains elusive, however.

The earliest philosophical discussions of dualism in the Greektradition to survive in full are those of Plato (c. 429–347BCE). Plato assumes a distinction between an invisible soul and avisible body, and argues for both the immortality of the soul, and forthe theory that the soul undergoes successive reincarnations. TheMeno, thePhaedo, and thePhaedrus allargue that humans exhibit knowledge that they could not have obtainedin their current life, presenting this as evidence for thesoul’s pre-existence. ThePhaedo adds several argumentsthat the soul will continue to exist after death. One such argumentappeals to the soul’s affinity with the eternal forms of which,according to Plato’s theory, material objects are mere copies(78b4–84b8).

Aristotle (384–322 BCE) develops a very different theory of thesoul. In multiple texts, including thePhysics,Metaphysics, andDe Anima, Aristotle analysesmaterial substances into the matter they are composed of and the formthat organises that matter. For example, Socrates is composed of somematter, his flesh and bones, organised by the form of a human being.This theory has come to be known as ‘hylomorphism’ fromthe Greek for matter (hyle) and form (morphe).

Aristotle identifies the soul of a living creature with its form, andhe argues, contra Plato, that forms cannot exist separately from thematerial they organise. Aristotle must therefore reject the view thatthe soul can survive without the body. However, Aristotle also arguesthat one part of the soul, the intellect, is immaterial. He reasonsthat a material organ is sensitive only to certain things, just as theeye is sensitive to light but not sound, whereas the intellect,according to Aristotle, is sensitive to all forms (De Anima429a10–b9). Commentators debate whether this means that, forAristotle, the intellect can exist without the body, even if theentire soul cannot.

Most Western philosophers from antiquity well into the modern eraembrace dualist theories descended from those of Plato and Aristotle.A third influential Greek tradition for our topic is Epicureanism.Epicurus (341–270 BCE) following the pre-Socratic Democritus (c.460–370 BCE) argued that the ‘soul’ is really acollection of physical atoms that disperse at death (Letter toHerodotus 10.65). Though its influence waned in late antiquity,Epicurean materialism underwent a revival in modernity led by figuresranging from Hobbes to Marx and influenced the development ofcontemporary materialism.

Of the other principal Greek schools, the Stoics described the soul ascomposed of a special kind of spiritual matter, ‘pneuma’,which pervades the universe; a view that can be seen as anticipatingcontemporary panpsychism. The Sceptics, Academic and Pyrrhonist,attempted to suspend judgment about such questions.

2.3 Dualism in the Abrahamic World

A factor shaping philosophical developments in the Western half ofEurasia and in Africa in late antiquity was the expansion of theAbrahamic faiths. This gave dualism a new intellectual context, andone that continues to shape philosophical discussions today (e.g.Warren, Murphey and Maloney 1998; Van Inwagen and Zimmerman 2007;Farris and Leidenhag 2024). A tradition of harmonising Greekphilosophy with Jewish scripture reached an early apex in the firstcentury CE in the work of Philo of Alexandria, who drew heavily onPlatonist approaches to the soul. Early Christian thinkers, mostfamously St Augustine (354–340), also adopted versions ofPlato’s dualism. Some scholars also credit Augustine withintroducing the conception of the soul as a subjective inner space, anidea that becomes important in modern discussions (Cary 2000).

Arabic-Islamic philosophy adopted a similar approach beginning with AlKindi in the 9th century (Adamson 2018). Thinkers in this traditiontend to favour a synthesis of (neo-)Platonic and Aristotelian theoriesof the soul. One influential contribution was Al Farabi’s (c.870–950) theory of the active intellect: a cosmic intellect thatstands to the human intellect as the sun stands to the eye. Thistheory was further developed by Avicenna (c. 890–1037) andformed the basis for Averroes’ (1126–1198) doctrine of the‘unity of the intellect’: the thesis that all humans sharea single intellect. Averroes’s doctrine generated controversy bycasting doubt on the idea of an individual afterlife. Another notablecontribution is Avicenna’s ‘floating man’ thoughtexperiment, which is sometimes regarded as a precursor to similarthought experiments in Descartes.

The philosophers of the Latin West inherited this synthesis ofPlatonic and Aristotelian dualism. A group at the University of Parisknown as the ‘Latin Averroists’ even adoptedAverroes’ doctrine of the unity of the intellect. The leadingfigures of the two main strands of scholastic philosophy, ThomasAquinas (1225–1274) and Duns Scotus (c. 1266–1308), bothopposed Averroes’ view, however, with Aquinas dedicating apolemical treatise to the topic (Adams 1992). At the same time,Aquinas also objects to the equation of the survival of the soul withthe survival of the self, asserting ‘my soul is not me’(Commentary on 1 Corinthians, 21:33–4). Commentors disagreeabout what this means for Aquinas’s understanding of anindividual afterlife (De Haan and Dahm 2019).

While Aquinas and Scotus agree on the general hylomorphic dualistframework and in their opposition to Averroes, they disagree on otherissues, especially whether the soul is the only substantial formorganising the matter of the body. Aquinas argues that one substancecan have only one substantial form. Scotus argues that the complexityof living beings requires multiple substantial forms (Cross 1998,47–76).

Not all early Abrahamic philosophers embrace straightforwardly dualistviews. The Church father Tertullian (c. 155–220 CE) and themedieval Jewish philosopher Solomon ibn Gabirol (c.1021/1022–1058/1070) both argue that the soul is, in a sense,material (Kitlzer 2013; Pessin 2013). Tertullian and Ibn Gabirol areat most ambiguous materialists, however. The former is influenced bythe Stoic idea that the soul is composed of a special kind of matterwith fundamentally mental characteristics, while Ibn Gabirol posits adistinctive kind of ‘incorporeal matter’ to serve as thematerial component of spiritual beings. The first philosopher tocombine the worldview of an Abrahamic religion with an unambiguouslymaterialist response to the mind-body problem may be Hobbes(1588–1679) in the Early Modern period (Weir 2022,116–117).

2.4 Dualism and Mechanistic Science

Early Modern philosophy also sees a major development in approaches todualism pioneered by Descartes (1596–1650). In addition toadvancing arguments for dualism that remain influential today,Descartes instigated two shifts in the way philosophers tend tounderstand dualism. First, in contrast to his Aristotelianpredecessors, he combined dualism with a new mechanistic conception ofthe natural world of which he was a pioneer. Secondly,while earlier philosophers in the West tend torest their arguments for the immateriality of the mind on theintellect, Descartes shifts the focus to consciousness, which he takesto include not just intellectual activity but also sensoryawareness. It is also in the context of mechanisticscience that the problem of mind-body interaction gains its status asthe leading objection to dualism.

Descartes argues that mind and body are distinct substancescharacterised by thought (which for Descartes, includes all consciousmental states) and extension respectively. By a‘substance’, Descartes means something that can exist byitself (Weir 2021a, 281–287). This theory, presented in all ofDescartes’ major works, has served as a standard starting pointfor discussions of the mind-body problem ever since.

Descartes’ successors challenge various aspects of his dualisttheory. Elizabeth of Bohemia (1596–1552) questioned whetherDescartes can explain how mind and body interact. Leibniz(1646–1714) and Berkeley (1685–1753) both attempted toreduce the material half of Descartes’ ontology to the mentalhalf, thereby inaugurating a modern tradition of idealist theories.Hume (1711–1776) substituted a bundle of fleeting perceptionsfor the Cartesian mind in a way reminiscent of, and possiblyinfluenced by, earlier Buddhist theories (Gopnik 2009). Furtherdetails on these debates appear below.

Nonetheless, dualist theories resembling Descartes’ remainedpopular. In his 1949 book, The Concept of Mind, Gilbert Ryle was ableto describe Cartesian dualism as the ‘official doctrine’to which ‘most philosophers, psychologists and religiousteachers subscribe, with minor reservation’ (Ryle 1949, 1). Notlong after the this, however, any such consensus had evaporated. Andalthough Ryle’s book is often seen as marking the moment whenthis shift took place, anti-dualist sentiment had been growing forsome time. Writing in 1930 Arthur Lovejoy states:

The last quarter-century, it may fairly confidently be predicted, willhave for future historians of philosophy a distinctive interest andinstructiveness as the Age of the Great Revolt against Dualism.(Lovejoy 1930, 1)

If the long-standing predominance of dualism had been under threat forseveral decades before Ryle, a stable alternative had not yet beenfound. The leading alternatives to dualism in the first half of thetwentieth century were neutral monism, phenomenalism, andbehaviourism, all of which remained minority positions. It is only inthe second half of the twentieth century that contemporary forms ofmaterialism came to predominate, beginning with U. T. Place (1956) andJ. J. C. Smart (1959).

The ascendance of materialism appears to have been due, in part, tothe mechanistic conception of nature that Descartes had helpedestablish. According to the mechanist, the physical world is, as itwould now be expressed, ‘causally closed’. This means thateverything that happens follows from and is in accord with the laws ofphysics. Descartes made an exception to accommodate mental causation.If one does not make such an exception, however, the mechanistictheory seems to make the mind an epiphenomenon: that is, it is aby-product of the physical system which has no influence back on it(see Huxley 1893).

While epiphenomenalism has its supporters, many philosopher have foundit implausible to claim such things as the following; the pain youfeel when you stub your toe, the visual sensations you have when yousee a ferocious lion bearing down on you, or the conscious sense ofunderstanding you have when you read these words – all havenothing directly to do with the way you respond. One way to avoid thisconclusion is to adopt the materialist hypothesis that one’smental states are one and the same as the physical causes ofone’s behaviours. David Papineau (2001) argues that it is theemergence of clear-cut evidence for closure under physics, even in thebodies of living creatures, that accounts for the rise of materialismin the 1950s and 1960s.

In the period since, the philosophy of mind has been characterised inlarge part by attempts to avoid dualism and vindicate materialism.Even so, some distinguished neuroscientists, such as CharlesSherrington (1951), Wilder Penfield (1975) and John Eccles (1994)continued to defend dualism throughout the second half of thetwentieth century. Several influentialphilosophers also presented arguments for dualism during this period,most prominently thinkers like Alvin Plantinga (1970) and RichardSwinburne (1986) who specialise in philosophy of religion, but alsoothers including Saul Kripke (1972/1989) and Karl Popper (Popper 1963,395–408; cf. Sellars 1954; O’Hear 2025).

Towards the end of the century, a series of challenges to materialismfrom a naturalistic perspective led to a revival of property dualismin mainstream philosophy of mind (e.g. Jackson 1982; Chalmers 1996;Kim 2005). As a result, a widely accepted opinion in the first decadesof the present century has held that although substance dualism is nolonger a respectable option, property dualism is an important positionthat must be taken seriously (see Weir 2023, 31–33). The ideathat property dualism is preferable to substance dualism is itselfregularly challenged, however (Francescotti 2001; Searle 2002;Zimmerman 2010; Schneider 2012; Lycan 2013; Robinson 2016; Weir2023).

3. Varieties of Dualism

One natural way to divide up kinds of dualism is in terms of whatsorts of things one chooses to be a dualist about. The most commoncategories lighted upon for these purposes are substance and property,giving one substance dualism and property dualism. A second way is interms of the sorts of causal influence between mind and body onerecognises. Interactionism is the view that mind and body act causallyon one another, epiphenomenalism says that that body acts on mind butmind does not act on body, and parallelism says that mind and body donot interact. This section reviews these distinctions and sayssomething about where hylomorphic dualism fits in.

3.1 Substance Dualism

In around the 1970s it became standard practice to draw a distinctionbetween ‘substance dualism’ and ‘propertydualism’ (Weir 2023, 33). Despite their widespread usage,however, these terms are rarely defined precisely. It is agreed thatby ‘substance dualism’ we mean the view that minds andbodies are fundamentally distinct kinds of substances, and that thisis the kind of view exemplified by Plato, Augustine, and Descartes,and resisted by some more recent dualists such as Jackson (1982) andKim (2005). What exactly ‘substance’means in this contextis often left vague, however.

Two traditional senses of ‘substance’ help clarify what isdistinctive of substance dualism. The first defines a substance as anindependent entity: something that can exist by itself (Westphal 2016,2–3; Weir 2023, 38–44). Substances on this view contrastwith properties, insofar as properties depend on their bearers fortheir existence. The second defines a substance as a unitary entitythat persists through time (Benovsky 2009). Substances on this viewcontrast with Buddhist or Humean bundles. (To persist through time inthe relevant sense might require that a substance be ‘whollypresent’ at each moment of its existence, in other words, thatitendures rather thanperdures, in the technical sense of those times. However, theidea of a substance as a persisting entity predates the the technicaldistinction between endurance and perdurance.) Paradigmaticsubstance dualists such as Plato, Augustine, and Descartes appear toaffirm that the mind is an immaterial substance in both senses: aunitary, persisting entity, which is capable of disembodiment and, tothat extent, has independent existence.

The two definitions of substance are logically independent, so someonemight endorse substance dualism in one sense but not the other. Forexample, Martine Nida-Rümelin (2012) defends a view whichplausibly qualifies as substance dualism in the sense that it posits aunitary, immaterial mind, but not in the sense that the mind can existindependently. Care must therefore be taken to be clear about what onemeans when one refers to a position as ‘substancedualism’. Nida-Rümelin chooses to use the term‘subject-body dualism’ over ‘substancedualism’ for this reason.

It is also sometimes assumed that a substance dualist must positsomething like a Lockean ‘substratum’ or a ‘thinparticular’, a component that must be combined withsomething’s properties to yield an object. However, it is lessclear that paradigmatic substance dualists posit immaterial substancesin this sense. For example, Descartes argues explicitly that the mindis a substance in the sense that it exists independently (with thequalification that nothing can exist without God), and he alsopresents the mind as a unitary (indeed indivisible) persisting entity.But Descartes does not obviously posit anything resembling a Lockeansubstratum (Markie 1994, 75–6; Broackes 2006, 160–62;Madell 2010, 52–56; Weir 2021a, 280–1).

Philosophers sometimes use ‘substance dualism’ to refer tothe kind of dualism that posits an immaterial self as opposed toimmaterial sensations, thoughts, and similar. This is a reasonableusage insofar as most philosophers take the view that if there areimmaterial selves, these will qualify as substances and that if thereare immaterial mental substances, these will be selves.

However, there is logical space for forms of dualism on which the selfis immaterial, in the sense that it consists in a complex successionof nonphysical properties, but is not independent, unitary, orpersisting. Likewise, there is logical space for forms of dualism onwhich the mind is an immaterial substance that does not, by itself,qualify as a person or self. Aquinas’s hylomorphic dualism,described above, may count as an example of the latter. To thisextent, the use of ‘substance dualism’ for forms ofdualism that posit an immaterial self may be misleading.

It is generally accepted that substance dualism is the kind of dualismthat predominates through most of the history of philosophy, and thatmay form part of the way humans naturally conceive of themselves(Bloom 2009). This makes sense, insofar as the traditional idea of aself or soul that survives bodily death is naturally be taken tosuggest a unitary, persisting and independent entity (Weir 2023,84–7). On the other hand, Buddhist philosophers have oftencombined belief in disembodied survival and reincarnation with theview of the self as a bundle of fleeting events.

Finally, ‘substance dualism’ is sometimes usedinterchangeably with ‘Cartesian dualism’. However, somesubstance dualists are keen to distinguish their theories fromDescartes’s. E. J. Lowe (2006) for example, is a substancedualist, in the following sense. He holds that a normal human beinginvolves two substances, one a body and the other a person. The latteris not, however, a purely mental substance that can be defined interms of thought or consciousness alone, as Descartes claimed. Whilethere is widespread agreement that substance dualism of some iswidespread in the history of ideas, it is less clear that this is trueof Cartesian dualism in a narrower sense (Hodge 2008).

The definitions given here do not exhaust those that have beenappealed to in discussions of substance dualism. Lowe himself favoursa distinctive definition in terms not of independence withoutqualification, but independence of identity. Swinburne (2019, 13)defines a substance merely as ‘a component of the world; aparticular object or collection of objects.’

3.2 Property Dualism

Two senses of the term ‘property dualism’ have currency incontemporary philosophy. The first names a kind of nonreductivematerialism and therefore not a form of dualism in the sense thatcontrasts with materialism. The second names a kind of dualism in thesense that contrasts with materialism, but that aims to avoid theperceived excesses of substance dualism. We will call the first view‘predicate dualism’ for the sake of clarity.

Predicate dualism is the theory that mental predicates are (a)essential for a full description of the world and (b) not reducible tophysicalistic predicates, in a sense of ‘reduction’defined by Ernst Nagle (1961). For a mental predicate to be reduciblein the sense in question, there must be bridging laws connecting typesof mental states to types of physical states in such a way that allstatements about mental states will be logically entailed byappropriate statements about physical states.

A standard example is the relationship between water and H₂O. It iswidely accepted that something is water if and only if it is H₂O. Itis therefore plausible that every statement about water is logicallyentailed by some statement about H₂O, meaning that any theoryconcerning water can be reduced, in Nagel’s (1961) sense, to atheory about H₂O. (An apparent exception is statements that create‘intensional’ contexts like ‘Shakespeare knew thatwater quenches thirst’. A standard response is that‘water’ cannot be replaced with ‘H₂O’ hereonly insofar as the sentence really concerns the mode of presentationunder which Shakespeare thinks of water, rather than wateritself.)

Many terms of the special sciences (that is, any science exceptphysics) are not reducible in this way. Not every hurricane or everyinfectious disease, let alone every devaluation of the currency orevery coup d’etat has the same constitutive structure. Thesethings are defined more by what they do than by their composition orstructure. Such things are multiply realizable; they may beconstituted by different kinds of physical structures under differentcircumstances. Because of this, one could not replace these terms bysome more basic physical description and still convey the sameinformation. There is no particular description, using the language ofphysics or chemistry, that would do the work of the word‘hurricane’, in the way that ‘H₂O’ would dothe work of ‘water’.

It is widely agreed that many, if not all, psychological states aresimilarly irreducible, and so psychological predicates are notreducible to physical descriptions. This is what is meant by predicatedualism. The classic source for irreducibility in the special sciencesin general is Fodor (1974), and for irreducibility in the philosophyof mind, Davidson (1971).

Predicate dualism is perfectly compatible with materialism. Eventhough the term ‘pain’, for example, cannot be replaced byany term from physics or chemistry, it could still be the case thatevery particular pain – every pain ‘token’, as it isexpressed – is identical with some physical event in thenervous system. That is how things are on Davidson’s theory.

The final decades of the twentieth century saw increasing interest inthe stronger position which we call property dualism. Whereaspredicate dualism says that there are two essentially different kindsof predicates in our language, property dualism says that there aretwo essentially different kinds of property out in the world.

Genuine property dualism occurs when, even at the individual level,the ontology of physics is not sufficient to constitute what is there.The irreducible language is not just another way of describing whatthere is, it requires that there be something more there than wasallowed for in the initial ontology. Until the early part of thetwentieth century, it was common to think that biological phenomena(‘life’) required property dualism (an irreducible‘vital force’), but nowadays the special physical sciencesother than psychology are generally thought to involve only predicatedualism.

In the case of mind, property dualism is usually defended by those whoargue that the qualitative nature of consciousness is not merelyanother way of categorising states of the brain or of behaviour, but agenuinely novel phenomenon. Three classic defences of property dualismare Jackson (1982), Chalmers (1996) and Kim (2005). These works arguethat consciousness involves properties above everything in theontology of the physical science. At the same time, they refrain frompositing immaterial substances.

It should be noted that Chalmers (2010, 139) has clarified that heintends ‘property dualism’ to entail that there arenonphysical properties whilst remaining neutral on nonphysicalsubstances, and he has since expressed a preference for substancedualism over property dualism (Chalmers 2016, 24), while Jackson(2003) has abandoned property dualism in favour of materialism.

3.3 Interactionism

Interactionism is the view that mind and body – or mental eventsand physical events – causally influence each other. That thisis so is one of our common-sense beliefs, because it appears to be afeature of everyday experience. The physical world influences myexperience through my senses, and I often react behaviourally to thoseexperiences. My thinking, too, influences my speech and my actions.There is, therefore, a natural prejudice in favour of interactionism.It has been claimed, however, that it faces serious problems.

The simplest objection to interaction is that, in so far as mind andbody are of radically different kinds from each other, they lack thatcommunality necessary for interaction. It is generally agreed that, inits most naive form, this objection to interactionism rests on a‘billiard ball’ picture of causation: if all causation isby impact, how can the material and the immaterial impact upon eachother? But if causation is either by a more ethereal force or energyor only a matter of constant conjunction, there would appear to be noproblem in principle with the idea of interaction of mind andbody.

Even if there is no objection in principle, there may be a conflictbetween interactionism and some basic principles of physical science.For example, mind-body interaction seems to require that causal powerflows in and out of the physical body in a way that would conflictwith the conservation of energy, a fundamental scientific law.

Defenders of interactionism have challenged the relevance of theconservation principle in this context. The conservation principlestates that ‘in a causally isolated system the total amount ofenergy will remain constant’. Whereas ‘[t]heinteractionist denies…that the human body is an isolatedsystem’, so the principle is irrelevant (Larmer 1986, 282; thisarticle presents a good brief survey of the options). This approachhas been termed conditionality, namely the view that conservation isconditional on the physical system being closed, that is, that nothingnon-physical is interacting or interfering with it, and, of course,the interactionist claims that this condition is, trivially, notmet.

That conditionality is the best line for the dualist to take, and thatother approaches do not work, is defended in Pitts (2019) and Cucu andPitts (2019). This, they claim, makes the plausibility ofinteractionism an empirical matter which only close investigation onthe fine operation of the brain could hope to settle. Papineau (2001)argues that such evidence was already clear cut in the 1960s. Cucu(2023), by contrast, claims to find critical neuronal events which donot have sufficient physical explanation even today. This claimclearly needs further investigation.

Robins Collins (2011) has claimed that the appeal to conservation byopponents of interactionism is something of a red herring becauseconservation principles are not ubiquitous in physics. He argues thatenergy is not conserved in general relativity, in quantum theory, orin the universe taken as a whole. Why then, should we insist on it inmind-brain interaction?

Most discussion of interactionism takes place in the context of theassumption that it is incompatible with the physical world’sbeing ‘causally closed’. This is a very naturalassumption, but it is not justified if causal overdetermination ofbehaviour is possible. There could then be a complete physical causeof behaviour, and a mental one. The strongest intuitive objectionagainst overdetermination is clearly stated by Mills (1996: 112), whois himself a defender of overdetermination.

For X to be a cause of Y, X must contribute something to Y. The onlyway a purely mental event could contribute to a purely physical onewould be to contribute some feature not already determined by a purelyphysical event. But if physical closure is true, there is no featureof the purely physical effect that is not contributed by the purelyphysical cause. Hence interactionism violates physical closure afterall.

Mills says that this argument is invalid, because a physical event canhave features not explained by the event which is its sufficientcause. For example, ‘the rock’s hitting the window iscausally sufficient for the window’s breaking, and thewindow’s breaking has the feature of being the thirdwindow-breaking in the house this year; but the facts about priorwindow-breakings, rather than the rock’s hitting the window, arewhat cause this window-breaking to have this feature.’

The opponent of overdetermination could perhaps reply that theprinciple applies, not to every feature of events, but to a subgroup– say, intrinsic features, not merely relational or comparativeones. It is this kind of feature that the mental event would have tocause, but physical closure leaves no room for this. These matters arestill controversial.

Lowe (2008) proposes a different strategy for reconciling mentalcausation with the empirical evidence for closure under physics. Hesuggests that physical causes always bring about the effects that wewould expect given the laws of physics. But certain physical causes inthe brain do so indirectly, by bringing about an intermediate mentalstate that in turn causes the ordinary physical effect. The mentalstate and its physical cause are simultaneous, so that there is notemporal gap in the causal sequence, allowing the mental state tobring about its physical effect in a way that is invisible toscientific observation.

The main objection to Lowe’s proposal is that it seems torequire an absurd coincidence, such that the effect of every mentalstate just happens to be the effect one would expect its proximatephysical cause to bring about by itself under other circumstances.Lowe (2008, 77) dismisses this objection, questioning whether it makessense to speak of a coincidence at the level of causal laws. Analternative objection says that Lowe must posit a causal theory thatbreaches ordinary standards of theory choice by sacrificing simplicityfor no gain in strength. Ordinarily, if two causal theories have equalexplanatory power, we favour the one that is simpler. This principlewould lead us to favour epiphenomenalism over Lowe’s proposal(Weir 2021b).

The problem with closure of physics may be radically altered ifphysical laws are indeterministic, as quantum theory seems to assert.If physical laws are deterministic, then any interference from outsidewould lead to a breach of those laws. But if they are indeterministic,interference might produce a result that has a probability greaterthan zero, and so be consistent with the laws.

Because it involves assessing the significance and consequences ofquantum theory, this is a difficult matter for the non-physicist toassess. Some argue that indeterminacy manifests itself only on thesubatomic level, being cancelled out by the time one reaches even verytiny macroscopic objects: and human behaviour is a macroscopicphenomenon. Others argue that the structure of the brain is so finelytuned that minute variations could have macroscopic effects, rather inthe way that, according to ‘chaos theory’, the flapping ofa butterfly’s wings in China might affect the weather in NewYork. (For discussion of this, see Eccles (1980; 1987), and Popper andEccles (1977).) Still others argue that quantum indeterminacymanifests itself directly at a high level, when acts of observationcollapse the wave function, suggesting that the mind may play a directrole in affecting the state of the world (Hodgson 1988; Stapp1993).

3.4 Epiphenomenalism

Epiphenomenalism is the theory that mental events are caused byphysical events, but have no causal influence on the physical. Theview was given currency by the biologist Thomas Huxley (1893), partlyas a result of his observations of reflex responses in frogs. Anancient precursor may be found in the Yoga-Samkhya view that the soul(purusha) consists in pure awareness and has no effect on thenatural world (prakriti) (Schweizer 2019).

Epiphenomenalism does not avoid the problem of how two fundamentallydifferent categories of thing might interact (Green 2003,149–51). If it is mysterious how the non-physical can have it inits nature to influence the physical, it ought to be equallymysterious how the physical can have it in its nature to producesomething non-physical. But epiphenomenalism does promise to avoid thedistinctive problems associated with an immaterial mind acting on amaterial body.

There are at least three serious problems for epiphenomenalism. First,as indicated in section 1, epiphenomenalism is profoundlycounterintuitive. What could be more apparent than that it is the painthat you feel that makes you cry, or the visual experience of theboulder rolling towards you that makes you run away? At least one cansay that epiphenomenalism is a fall-back position: it tends to beadopted because other options are held to be unacceptable.

A second problem, pressed by William James (1890), is that, if mentalstates do nothing, there appears to be no reason why they should haveevolved. This objection ties in with the first: the intuition therewas that conscious states clearly modify our behaviour in certainways, such as avoiding danger, and it is plain that this would makethem very useful from an evolutionary perspective.

Jackson (1982) replies to this objection by saying that it is thebrain state associated with pain that evolves for this reason: thesensation is a by-product. Evolution is full of useless or evenharmful by-products. For example, polar bears have evolved thick coatsto keep them warm, even though this has the damaging side effect thatthey are heavy to carry.

Jackson’s point is true in general, but does not obviously applyto the case of mind. The heaviness of the polar bear’s coatfollows directly from those properties and laws which make it warm:one could not, in any simple way, have one without the other. But withmental states, dualistically conceived, the situation is the opposite.The laws of physical nature which, the mechanist says, make brainstates cause behaviour, in no way explain why brain states should giverise to conscious ones. The laws linking mind and brain are what Feigl(1958) calls nomological danglers, that is, brute facts added onto thebody of integrated physical law. Why there should have beenby-products of that kind seems to have no obvious evolutionaryexplanation.

The third problem concerns the rationality of belief inepiphenomenalism, via its effect on the problem of other minds. It isnatural to say that I know that I have mental states because Iexperience them directly. But how can I justify my belief that othershave them? The simple version of the ‘argument fromanalogy’ says that I can extrapolate from my own case. I knowthat certain of my mental states are correlated with certain pieces ofbehaviour, and so I infer that similar behaviour in others is alsoaccompanied by similar mental states.

Many hold that this is a weak argument because it is induction fromone instance, namely, my own. The argument is stronger if it is not asimple induction but an ‘argument to the bestexplanation’. I seem to know from my own case that mental eventscan be the explanation of behaviour, and I know of no other candidateexplanation for typical human behaviour, so I postulate the sameexplanation for the behaviour of others. But if epiphenomenalism istrue, my mental states do not explain my behaviour and there is aphysical explanation for the behaviour of others. It is explanatorilyredundant to postulate such states for others. I know, byintrospection, that I have them, but is it not just as likely that Ialone am subject to this quirk of nature, rather than that everyoneis?

For more detailed treatment and further reading on this topic, see theentryepiphenomenalism.

3.5 Parallelism

Epiphenomenalists wishes to preserve the integrity of physical scienceand the physical world, and appends those mental features that theycannot reduce. Parallelists preserve both realms intact, but deny allcausal interaction between them. The mental and physical realms run inharmony with each other, but not because their mutual influence keepseach other in line. That the two should behave as if they wereinteracting would seem to be a bizarre coincidence. This is whyparallelism has tended to be adopted only by those – likeLeibniz – who believe in a pre-established harmony, set in placeby God.

The progression of thought can be seen as follows. Descartes believesin a more or less natural form of interaction between immaterial mindand material body. Malebranche thought that this was impossiblenaturally, and so required God to intervene specifically on eachoccasion on which interaction was required. Leibniz decided that Godmight as well set things up so that they always behaved as if theywere interacting, without particular intervention being required.

Outside such a theistic framework, the theory may seem incredible.Even within such a framework, one might sympathise withBerkeley’s instinct that once genuine interaction is ruled outone is best advised to allow that God creates the physical worlddirectly, within the mental realm itself, as a construct out ofexperience. For an argument that even Berkeley’s subjectiveidealism falls foul of the problem of mind-body interaction, see Weir(2021b).

3.6 Hylomorphic Dualism

As noted in section 1.2, hylomorphism is the view that materialsubstances can be explained in terms of two principles, the matterthey are composed of, and the form that organises that matter:Socrates is composed of flesh and bones, organised by the form of ahuman being. Hylomorphists since Aristotle have identified that soulof a living creature with its form. This need not entail any form ofmind-body dualism. For a hylomorphist is at liberty to take the viewthat a human is a wholly physical composite of matter and form, like aplant or a rock. However, Aristotle argues that the human soul has animmaterial part, the intellect, making him to that extent a kind ofdualist. More thoroughgoing forms of dualism can be found among laterhylomorphists such as Thomas Aquinas, who states that the soul is animmaterial substance (Summa Theologiae, Q 75, A2).

It is no surprise, therefore, that some contemporary hylomorphistsdescribe themselves as ‘hylomorphic dualists’ respectingthe mind-body problem (e.g. Oderberg 2005). There is less agreementabout two further questions: is hylomorphic dualism a kind ofsubstance dualism, property dualism, or a third theory of neitherkind? And where does hylomorphic dualism stand on the issue ofmind-body interaction?

It might seem clear that Aquinas, at least, should be understood as ahylomorphic substance dualist. For he himself identifies the soul asan immaterial substance by name, and describes the soul as a unitary,persisting entity that is capable of disembodied existence.

At least some scholars are happy to class certain versions ofhylomorphic dualism as hylomorphic substance dualism (Rickabaugh andMoreland 2023, 326–8). At the same time, there are severalreasons why commentators have resisted the idea that evenAquinas’s position should be described this way.

First, although Aquinas identifies the soul as a substance, hedescribes it as an incomplete substance (Skrezypek 2021). Secondly,Aquinas does not identify theself as an immaterialsubstance, and may deny that the self can exist by itself (De Haan andDahm 2019). Thirdly, substance dualism is naturally understood as aview on which both body and soul are substances. However, for Aquinas,the human body depends on the soul for its existence. For this reason,if might make greater sense to think of Aquinas as a kind of inverseproperty dualist, for whom a human is an immaterial substance withmaterial properties (Weir 2023, 138–9).

Proponents of hylomorphic dualism contend that it has an advantageover other kinds of dualism respecting the interaction problem. As wehave seen, some versions of the interaction problem rest on the claimthat it is mysterious how an immaterial mind and a material body couldinteract. Hylomorphists can reply that interaction between mind andbody is just one instance of the kind of interaction between form andmatter that goes on throughout nature and is therefore unmysterious(Feser 2006, 223; 2024, 506–8).

This proposal is not necessarily pertinent to the most influentialversion of the interaction problem however, the contention thatempirical evidence shows the material world to be causally closed. Anopponent of hylomorphic dualism might contend that either the soul, onthis view, either has no effect on bodily behaviour or, absurdly,causes only those behaviours that a mechanist would expect if therewere no such thing as the soul. A natural response for hylomorphicdualists would be to reject the principle of causal closure itself,along with the mechanistic, bottom-up picture of the material worldthat this principle exemplifies. However, if the empirical case forclosure under physics is less than clear cut this may be of comparablehelp to non-hylomorphic dualists, calling into question whetherhylomorphic dualism has a special advantage here.

4. Arguments for Dualism

The most influential arguments for dualism in contemporary philosophyfocus on consciousness, the fact that there is ‘something it islike’ to be a mentally endowed creature, in Thomas Nagel’s(1974) famous expression. Of these the most important are theknowledge argument and the conceivability argument. Two furthermotivations for dualism covered here are the argument from personalidentity, and a modern version of the Aristotelian argument. Importantmotivations for dualism not covered include arguments from free will(Goetz 2016), from tense (Pearson 2018), and from the unity ofconsciousness (Hasker 1999).

4.1 The Knowledge Argument

One category of arguments for dualism is constituted by the standardobjections against physicalism. Prime examples are those based on theexistence of qualia, one of the most important of which is theso-called ‘knowledge argument’. Because this argument hasits own entry (see the entryqualia: the knowledge argument), we will deal relatively briefly with it here.

The knowledge argument asks us to imagine a future scientist who haslacked a certain sensory modality from birth, but who has acquired aperfect scientific understanding of how this modality operates inothers. This scientist – call him Harpo – may have beenborn stone deaf, but become the world’s greatest expert on themachinery of hearing: he knows everything that there is to know withinthe range of the physical and behavioural sciences about hearing.

Suppose that Harpo, thanks to developments in neurosurgery, has anoperation which finally enables him to hear. It is suggested that hewill then learn something he did not know before, which can beexpressed as what it is like to hear, or the qualitative or phenomenalnature of sound. These qualitative features of experience aregenerally referred to as qualia. If Harpo learns something new, he didnot know everything before. He knew all the physical facts before. Sowhat he learns on coming to hear – the facts about the nature ofexperience or the nature of qualia – are non-physical. Thisestablishes at least a state or property dualism. (See Jackson 1982;Robinson 1982.)

There are at least two lines of response to this popular butcontroversial argument (cf. Goff 2017, 64–74). First is the‘ability’ response. According to this, Harpo does notacquire any new factual knowledge, only ‘knowledge how’,in the form of the ability to respond directly to sounds, which hecould not do before. This essentially behaviouristic account isexactly what the intuition behind the argument is meant to overthrow.Putting ourselves in Harpo’s position, it is meant to be obviousthat what he acquires is knowledge of what something is like, not justhow to do something. Such appeals to intuition are always, of course,open to denial by those who claim not to share the intuition. Someability theorists seem to blur the distinction between knowing whatsomething is like and knowing how to do something, by saying that theability Harpo acquires is to imagine or remember the nature of sound.In this case, what he acquires the ability to do involves therepresentation to himself of what the thing is like. But thisconception of representing to oneself, especially in the form ofimagination, seems sufficiently close to producing in oneselfsomething very like a sensory experience that it only defers theproblem: until one has a physicalist gloss on what constitutes suchrepresentations as those involved in conscious memory and imagination,no progress has been made.

The other line of response is to argue that, although Harpo’snew knowledge is factual, it is not knowledge of a new fact. Rather,it is new way of grasping something that he already knew. He does notrealise this, because the concepts employed to capture experience(such as ‘looks red’ or ‘sounds C-sharp’) aresimilar to demonstratives, and demonstrative concepts lack the kind ofdescriptive content that allow one to infer what they express fromother pieces of information that one may already possess. A totalscientific knowledge of the world would not enable you to say whichtime was ‘now’ or which place was ‘here’.Demonstrative concepts pick something out without saying anythingextra about it. Similarly, the scientific knowledge that Harpooriginally possessed did not enable him to anticipate what it would belike to re-express some parts of that knowledge using thedemonstrative concepts that only experience can give one. Theknowledge, therefore, appears to be genuinely new, whereas only themode of conceiving it is novel.

Proponents of the argument respond that it is problematic to maintainboth that the qualitative nature of experience can be genuinely novel,and that the quality itself be the same as some property alreadygrasped scientifically: does not the experience’s phenomenalnature, which the demonstrative concepts capture, constitute aproperty in its own right? Another way to put this is to say thatphenomenal concepts are not pure demonstratives, like‘here’ and ‘now’, or ‘this’ and‘that’, because they do capture a genuine qualitativecontent. Furthermore, experiencing does not seem to consist simply inexercising a particular kind of concept, demonstrative or not. WhenHarpo has his new form of experience, he does not simply exercise anew concept; he also grasps something new – the phenomenalquality – with that concept. How decisive these considerationsare, remains controversial.

4.2 The Conceivability Argument

The conceivability argument comes in two forms: the disembodimentargument, originating in Descartes (Meditation V) and thezombie argument, made popular by Chalmers (1996; 2010). Thedisembodiment argument can be put as follows:

It is conceivable that one’s mind might exist withoutone’s body.
If it is conceivable that one’s mind might exist withoutone’s body then it is possible that one’s mind might existwithout one’s body.
Therefore, it is possible that one’s mind might existwithout one’s body.
Therefore, one’s mind is a different entity from one’sbody.

Descartes’ rationale for accepting premiss (1) can be found inMeditations I and II where he argues that one can coherently doubtthat anything exists apart from one’s present consciousexistence. Philip Goff summarises Descartes’ line of reasoningas follows:

The arms and legs you seem to see in front of you, the heart you seemto feel beating beneath your breast, your body that feels solid andwarm to the touch, all may be figments of a particularly powerfuldelusion. You might not even have a brain. … [Nonetheless] youknow for certain that you are a thing that has an experience as ofhaving arms and legs, a beating heart, a warm, solid body. (Goff 2010,124)

If one can coherently doubt the existence of anything beyondone’s conscious mind, then it is apparently conceivable thatone’s mind might exist without one’s body. For Descartes,premiss (2) rests on the principle that anything one can clearly anddistinctly conceive is possible.

Another important disembodiment argument appears in Kripke (1972,336–7). Unlike Descartes’ argument, which focusses on theconceivability that I, as a conscious mind, might exist without abody, Kripke starts with the claim that it is conceivable that aparticular pain ‘A’ could exist without the particularbrain state with which it is reputed to be identical.

Recent discussion has given greater weight to the second version ofthe conceivability argument, defended by Chalmers (1996, 94–9).Rather than focussing on the idea of a disembodied mind, Chalmersfocuses on the idea of a mindless body. More precisely, he focuses onthe idea of a ‘philosophical zombie’ understood as anexact duplicate of a conscious human being, without the consciousness.The zombie argument can be put as follows:

It is conceivable that a physical duplicate of some human shouldexist without consciousness (i.e. zombies are conceivable).
If it is conceivable that a physical duplicate of some humanshould exist without consciousness, then it is possible that aphysical duplicate of some human should exist without consciousness(i.e. if zombies are conceivable then zombies are possible).
Therefore, it is possible that a physical duplicate of some humanshould exist without consciousness (i.e. zombies are possible).
Therefore, consciousness is something over and above thephysical.

Chalmers (2002) distinguishes two senses in which premiss (1) seems tobe true. First, zombies are conceivable in the sense that we cannotrule out the possibility of such a scenario a priori: there is noapparent contradiction in the idea of a physical duplicate of a humanthat lacks consciousness. Secondly, zombies are conceivable in thesense that we seem to be able to positively imagine such a scenario insufficient detail to see that it is not contradictory: one can picturewhat it would be like for a zombie to exist. For Chalmers, the casefor premiss (2) consists in a theory of the relationship betweensemantics and modality to which we return below.

The zombie argument differs from the disembodiment argument becausethe hypothesis that the unaltered body could exist without the mind isnot the same as the suggestion that the mind might continue to existwithout the body, nor are they trivially equivalent. The zombieargument establishes only property dualism and a property dualistmight think disembodied existence inconceivable – for example,if they thought the identity of a mind through time depended on itsrelation to a body (e.g., Penelhum 1970).

There are two main responses to the conceivability argument, in eitherform. The first response claims that the scenario described in premiss(1) is not in fact conceivable. For example, an analyticalbehaviourist can argue both that the disembodiment scenario isconceptually impossible, because the existence of mental states apriori entails the existence of certain behavioural states, and thatthe zombie scenario is conceptually impossible because the existenceof the physical duplicate’s behavioural states a priori entailsthe mental states associate with those behaviours. In the context ofthe zombie argument, opponents of premiss (1) are known as‘type-A’ materialists. Chalmers attributes such a view toDennett (1991).

Most professional philosophers accept premiss (1) of the zombiesargument (Bourget and Chalmers 2023). Naturally, therefore, most ofthe discussion has concerned premiss (2).

The main challenge to premiss (2) says that conceivability is not areliable guide to possibility. A rationale of those who think thatconceivability is not a safe indication of possibility is that thereexist a posteriori necessary propositions which we can nonethelessconceive being false. For example, we seem to be able to conceive asituation in which Hesperus is not identical to Phosphorus or on whichwater is not H₂O. And yet if Kripke (1972/1980) is correct, these arenot real possibilities despite their apparent conceivability. Anotherway of putting this point is that there are many epistemicpossibilities which are conceivable because they are epistemicpossibilities, but which are not real possibilities.

The standard response to this objection is to provide a theory of whatis going in the kind of a posteriori necessities discussed by Kripke,and to show that the relationship between mind and body cannot be an aposteriori necessity of the relevant kind.

For example, Chalmers draws a distinction between two dimensions ofthe meaning of a term, the ‘primary intension’ and the‘secondary intension’. Take the case of‘water’. There is a sense in which we can imagine ascenario in which it turns out that water is not H₂O but XYZ. And yet,there is also a sense in which, following Kripke (1972/1980), we thinkit is impossible that anything but H₂O could be water. What is goingon here? Chalmer’s answer is that the term ‘water’has a primary intension, which is the function from the actual worldto whatever meets our everyday understanding of water: roughly, theclear, drinkable liquid in lakes and rivers etc. ‘Water’also has a secondary intension which is the function from a worldconsidered as counterfactual to whatever, in that world, shares theunderlying essence of water in the actual world.

The sense in which it is true that water could be XYZ is that thereare possible scenarios in which the clear drinkable liquid in lakesand rivers really is XYZ. Were such a scenario actually to obtain, wewould rightly say ‘water is XYZ’ because XZY is what theprimary intension of ‘water’ would pick out. The sense inwhich it is impossible that water could be XYZ is that, given theempirical fact that water is actually H₂O, the secondary intension of‘water’ picks out H₂O in all counterfactual scenarios.

While there are many details to fill in, the important point is thatwhen we seem to conceive of water not being H₂O, we do not conceive ofan impossible scenario. We conceive of a possible scenario in whichthe extension of the term ‘water’ is different. This canhappen because the primary and secondary intensions of‘water’ differ.

Might we not be doing something similar when we seem to conceive of aphilosophical zombie? Chalmers’ argues that this cannot be so.For it would require that the terms we use to describe consciousexperience have different primary and secondary intensions, and theydo not.

The primary intension of the term ‘pain’, for example,picks out a certain feeling – that of hurting – just asthe primary intension of ‘water’ picks out the cleardrinkable liquid in lakes and rivers. But the secondary intension of‘pain’ does not pick out some underlying essence thatmight be present without the primary-intension property of hurting, inthe way that the secondary intension of ‘water’ does pickout H₂O. Rather, the secondary intension of ‘pain’ picksout exactly the same thing as the primary intension: anything thatfeels like pain.

Another way of putting this is to say that what we mean by‘water’ is whatever has the actual underlying essence ofthe stuff that appears a certain way. Whereas what we mean by‘pain’ is just whatever appears (or feels) a certain way:the primary and secondary intensions of ‘pain’ and otherterms for conscious experiences are the same.

The upshot is that when we seem to conceive of a physical duplicate ofa conscious human without conscious experiences we can be confidentthat we are conceiving of a genuinely possible scenario. There is nopossibility that we are failing to recognise that the underlyingessence of consciousness is present in this scenario. For when we talkabout consciousness we are not talking about some underlying essencethat stands to our experiences as H₂O does to water but about theexperiences themselves.

Other strategies for defending the inference from conceivability topossibility have been put forward by Swinburne (1997, New Appendix C;2018), Goff (2017), and by Kripke (1972/1980) himself, among others.While the details differ, they share the basic structure, analysingwhat is going on in the kind of a posteriori necessity identified byKripke, and then showing that the relationship between mind and bodycannot be an instance of that kind of a posteriori necessity.

Two kinds of response exist. The first says that there is some otherreason why we are mistaken when we take ourselves to be able toconceive of disembodied minds or of ghosts. The most influentialversion of this response says that the relevant mental terms are, orbehave like, demonstratives or indexicals, which pick out theirreferent without conveying any information about them. This responseis especially powerful regarding Descartes’ originalarticulation of the disembodiment argument, which uses the indexical‘I’. For a disembodiment argument that does not usedemonstratives or indexicals, see Weir (2023, 103–6).

To wield the same response against a conceivability argument that doesnot use demonstratives or indexicals it is necessary to argue thatphenomenal concepts behave like demonstratives. We saw this kind ofresponse to the knowledge argument above. As in that case, the mainreply is that phenomenal concepts seem to capture the qualitativenature of their referents, in which case they are not relevantly likedemonstratives.

The other option is to argue that while there is no special reason whythe apparent possibilities described in the conceivability argumentmay turn out to be impossible, this could still be the case, simplybecause there is no strong connection between conceivability andpossibility. This response is sometimes expressed by saying that theentailment from mind to body or body to mind might be a ‘strongnecessity’ (Chalmers 2002, 36). For an argument that theexistence of strong necessities is itself a priori impossible, seeCleevely (2022).

4.3 The Argument from Personal Identity

There is a long tradition, dating at least from Reid (1785), ofarguing that the identity of persons over time is not a matter ofconvention or degree in the way that the identity of other (complex)substances is and that this shows that the self is a different kind ofentity from any physical body. Criticism of these arguments and of theintuitions on which they rest, running from Hume to Parfit (1970:1984), have left us with an inconclusive clash of intuitions.

A related argument which may have its first statement in Madell(1981), does not concern identity through time, but the consequencesfor identity of certain counterfactuals concerning origin. It can,perhaps, therefore, break the stalemate which faces the debate overdiachronic identity. The claim is that the broadly conventionalistways which are used to deal with problem cases through time for bothpersons and material objects, and which can also be employed in casesof counterfactuals concerning origin for bodies, cannot be used forsimilar counterfactuals concerning persons or minds.

Concerning ordinary physical objects, it is easy to imaginecounterfactual cases where questions of identity become problematic.Take the example of a particular table. We can scale counterfactualsuggestions as follows:

This table might have been made of ice.
This table might have been made of a different sort of wood.
This table might have been made of 95% of the wood it was made ofand 5% of some other wood.

The first suggestion would normally be rejected as clearly false, butthere will come a point along the spectrum illustrated from (i) to(iii) where the question of whether the hypothesised table would bethe same as the one that actually exists have no obvious answer. Itseems that the question of whether it ‘really’ is the sameone has no clear meaning: it is of, say, 75% the same matter and of25% different matter; these are the only genuine facts in the case;the question of numerical identity can be decided in any convenientfashion, or left unresolved. There will thus be a penumbra ofcounterfactual cases where the question of whether two things would bethe same is not a matter of fact.

Let us now apply this thought to conscious subjects. Suppose that agiven human individual had had origins different from those which hein fact had such that whether that difference affectedwho hewas was not obvious to intuition. What would count as such a casemight be a matter of controversy, but there must be one. Perhaps it isunclear whether, if there had been a counterpart to Jones’ bodyfrom the same egg but a different though genetically identical spermfrom the same father, the person there embodied would have been Jones.Some philosophers might regard it as obvious that sameness of sperm isessential to the identity of a human body and to personal identity. Inthat case imagine a counterpart sperm in which some of the moleculesin the sperm are different; would that be the same sperm? If onepursues the matter far enough there will be indeterminacy which willinfect that of the resulting body. There must therefore be somedifference such that neither natural language nor intuition tells uswhether the difference alters the identity of the human body; a point,that is, where the question of whether we have the same body is not amatter of fact.

How one is to describe these cases is, in some respects, a matter ofcontroversy. Some philosophers think one can talk ofvagueidentity orpartial identity. Others think that suchexpressions are nonsensical. There is no space to discuss this issuehere. It is enough to assume, however, that questions of how one isallowed to use the concept of identity effect only the care with whichone should characterize these cases, not any substantive matter offact. There are cases of substantial overlap of constitution in whichthat fact is the only bedrock fact in the case: there is nofurther fact about whether they are ‘really’ the sameobject. If there were, then there would have to be ahaecceitas orthisness belonging to andindividuating each complex physical object, and this we are assumingto be implausible if not unintelligible. (More about the conditionsunder whichhaecceitas can make sense will be foundbelow.)

One might plausibly claim that no similar overlap of constitution canbe applied to the counterfactual identity of minds. In GeoffreyMadell’s (1981) words:

But while my present body can thus have its partial counterpart insome possible world, my present consciousness cannot. Any presentstate of consciousness that I can imagine either is or is not mine.There is no question of degree here. (91)

Why is this so? Imagine the case where we are not sure whether itwould have been Jones’ body – and, hence, Jones –that would have been created by the slightly modified sperm and thesame egg. Can we say, as we would for an object with no consciousness,that the storysomething the same,somethingdifferent is the whole story: that overlap of constitution is allthere is to it? For the Jones body as such, this approach would do aswell as for any other physical object. But suppose Jones, inreflective mood, asks himself ‘if that had happened, would Ihave existed?’ There are at least three answers he might give tohimself. (i) I either would or would not, but I cannot tell. (ii)There is no fact of the matter whether I would or would not haveexisted: it is just a mis-posed question. (iii) In some ways, or tosome degree, I would have, and in some ways, or to some degree, Iwould not. The creature who would have existed would have had a kindof overlap of psychic constitution with me.

The third answer parallels the response we would give in the case ofbodies. But as an account of the subjective situation, it is arguablethat this makes no sense. Call the creature that would have emergedfrom the slightly modified sperm, ‘Jones2’. Is the overlapsuggestion that, just as, say 85% of Jones2’s original bodywould have been identical with Jones’, about 85% of his psychiclife would have been Jones’? That it would have beenlike Jones’ – indeed that Jones2 might have had apsychic life 100% like Jones’ – makes perfect sense, butthat he might have been to that degree, the same psyche – thatJones ‘85% existed’ – arguably makes no sense. Takethe case in which Jones and Jones2 haveexactly similar livesthroughout: which 85% of the 100% similar mental events do they share?Nor does it make sense to suggest that Jones might have participatedin the whole of Jones2’s psychic life, but in a rather ghostlyonly 85% there manner. Clearly, the notion of overlap ofnumerically identical psychic parts cannot be applied in the way thatoverlap of actual bodily part constitution quite unproblematicallycan.

This might make one try the second answer. We can apply the‘overlap’ answer to the Jones body, but the question ofwhether the minds or subjects would have been the same, has no clearsense. It is difficult to see why it does not. Suppose Jones found outthat he had originally been one of twins, in the sense that the zygotefrom which he developed had divided, but that the other half had diedsoon afterwards. He can entertain the thought that if it had been hishalf that had died, he would never have existed as a conscious being,though someone would whose life, both inner and outer, might have beenvery similar to his. He might feel rather guiltily grateful that itwas the other half that died. It would be strange to think that Jonesis wrong to think that there is a matter of fact about this. And howis one to ‘manage’ the transition from the case wherethere is a matter of fact to the case where there is not?

If the reasoning above is correct, one is left with only the firstoption. If so, there has to be an absolute matter of fact from thesubjective point of view. But the physical examples we have consideredshow that when something is essentially complex, this cannot be thecase. When there is constitution, degree and overlap of constitutionare inevitably possible. So the mind must be simple. Given that thebody is high complex, it seems to follow that the mind isimmaterial.

4.4 The Aristotelian Argument in Modern Form

Putting his anti-materialist argument outlined above, in section 1, invery general terms, Aristotle’s worry was that a material organcould not have the range and flexibility that are required for humanthought. His worries concerned the cramping effect that matter wouldhave on the range ofobjects that intellect couldaccommodate. Parallel modern concerns centre on the restriction thatmatter would impose on the range of rationalprocesses thatwe could exhibit. Some of these concerns are of a technical kind.Gödel, for example, believed that his famous theorem showed thatthere are demonstrably rational forms of mathematical thought of whichhumans are capable which could not be exhibited by a mechanical orformal system of a sort that a physical mind would have to be. Penrose(1990) has argued that Turing’s halting problem has similarconsequences. But there are other less technical and easier toappreciate issues. We will mention four ways in which physicalisttheories of thought seem vulnerable to attack by the dualist.

(a) At least since the time of Ryle’s (1949)Concept ofMind, it has been assumed that thinking can be handled in adispositionalist way; so only sensations or ‘raw feels’constitute a problem for the physicalist. There has been a rise orrevival of a belief in what is now calledcognitivephenomenology, that is, the belief that thoughts, of whateverkind – beliefs, desires, and the whole range of propositionalattitude state – are conscious in a more than behaviouralfunctional sense. This raises problems for physicalism, for, just asit is a problem that direct knowledge of ‘what it is like’to experience your sensations is ultimately hidden from anyone else,sowhat you are thinking is directly accessible onlyprivately, once it has been conceded that it has a phenomenology andnot just a functional manifestation.

(b) Anything purely physical operates solely according to physicallaws operating on its physical properties: it does not, at bottom,operate according to meanings, senses, or propositional content. As a‘thinking machine’, it is what Dennett (1987, 61) calls‘a syntactic engine’, where ‘syntax’ is used,somewhat extendedly, to signify merely the physical structure ofsymbols and the consequent rules of their operation, rather than theirmeaning. The issue is whether, under this constraint, one can give anaccount for meaningful communication and understanding at all.

(c) Physicalist theories of thought almost all focus on the model ofcomputing, and when it comes to making problem solving (as opposed tosimply calculating) computers, computation comes across what is knownas the Frame Problem. This is clearly expounded in Dennett (1984); seealso the entry onThe Frame Problem. The problem is that the ‘mechanical mind’ can only followinstructions, cannot see relevance that has not been strictly encoded.This is often expressed by saying it lacks ‘commonsense’.

(d) There is what has become known as ‘Benacerraf’sProblem’ (See his 1983; cf. Robinson 2011). Numbers, it wouldseem, are abstract objects, yet our intellects operate with them allthe time. How does a physical brain interact with an abstract entity?A similar problem could be raised for concepts in general; they areabstract, general entities, not physical particulars, yet they are themeat and drink of thinking. For a dualist about intellect there doesnot appear to be the same problem. The immaterial intellect isprecisely the sort of thing that can grasp abstract objects, such asnumbers and universals – in the Aristotelian context, theimmaterial intellect is the home of forms. (There is still the issueof how this intellectual capacity of the immaterial mind relates tosensory consciousness. According to Aristotle, perception is a whollyembodied process, but for modern dualists, sensory consciousness isnot material. In order to unify the perceptual and intellectualfunctions of the mind, traditional empiricists tended to be imagists,in their theory of thought, in order to assimilate the intellectual tothe sensory, but this assimilation is rejected by those who believe ina distinct cognitive phenomenology, as mentioned in (a) above.) Thedifficulty in accounting for the brain’s relation to abstractentities explains why most materialists tend to be nominalists, thusreducing thoughts to concrete particulars of some kind. (D. M.Armstrong in his (1978) is a striking exception to this, accepting anin re theory of universals.) But if you do not find eithernominalism or Armstrong’s causal-functional theory of thinkingconvincing, Plato’s idea in thePhaedo that theintellect must be such that it can have an affinity with immaterialthings may begin to look plausible.

We will not discuss (a) further, as it is discussed in section 5 ofthe entry onphenomenal intentionality, An immaterialist response to (d) can be found in Robinson (2011).

Both (b) and (c) seem to draw out the claim that a material systemlacks understanding. John Searle’s famous ‘ChineseRoom’ argument (Searle 1980; see also the entry on theChinese Room Argument) seems to support this conclusion, at least if the material systemtakes the form of a classical computer, manipulating symbols accordingto rules. Searle imagines himself in a room with a letter box throughwhich strings of symbols are posted in, and, following a book ofrules, he puts out symbols which the rules dictate, given the stringshe is receiving. In fact, Searle says, he has been conducting aconversation in Chinese, because the symbols are Chinese script, andthe rules those on which a Chinese computer might work, but he has notunderstood a word. Therefore, neither does a computer understand, sowe, understanding creatures, are not computers. If Searle is right,this is the end for the classical ‘syntactic engine’ as amodel for thought.

Another argument for the same conclusion is advanced by James Ross(2008, Ch. 6) and Edward Feser (2013). This argument contends that forthe kind of reasons given by Kripke (1982), nothing material can havean exact or unambiguous conceptual content. For example, nothing abouta machine can ever make it determinately true that it is engaging inaddition, rather than a distinct function, ‘quaddition’which yields the same results when x and y are smaller than somearbitrarily high number n, but that yield 5 otherwise. Since themachine’s internal operations can be interpreted in variousways, nothing about its physical configuration or computationalhistory uniquely fixes which rule it is following. If it malfunctionsand starts yielding quaddition outputs rather than addition outputs,the only thing that makes this count as a malfunction is extrinsicfactors such as its designers’ intentions or ourinterpretations. By contrast, human thought processes can have anexact or unambiguous conceptual content: it is really true that humanscan add rather than quuad. If so, it follows that human thoughtprocesses are not material.

A blow was struck against the computational theory of thought when, in2000, Fodor produced hisThe Mind Does Not Work That Way, inwhich he made clear his belief that the kind of computationalism thathe had been describing and developing ever since the 1970s only fitssub-personal informational processing, not conscious, problem solvingthought. Fodor had, in fact, always mentioned this reservation, buthis claim that what he was describing was ‘the Language ofThought’ led his readers generally to take him to be proposingan account of what we normally consider to be thinking, which is notrestricted to (even if it includes at all) sub-personal processes. Themodest view is entirely in line with his close colleagueChomsky’s claim that his – Chomsky’s –linguistic theories cannot touch the ‘creative use oflanguage’(See Baker, 2011).

A physicalist response to at least some of these challenges is to saythat they apply only to the classical computing model, and are avoidedby connectionist theories. Classical computing works on rules ofinference like those of standard logic, but connectionism is rather aform of associationism, which is supposedly closer to the way in whichthe brain works. (See the entry on Connectionism.) The latest versionof this – ‘Deep Learning’ – has provenunexpectedly powerful and underlies all the major advances of AI inrecent years, from image generation to chatbots. But Gary Marcus (2018– see Other Internet Resources) and others have pointed out theways in which these impressive machines are quite different from humanthought. Marcus points to ten significant differences, but the twomost easy to capture briefly are (i) ‘deep learning’ isdata hungry. We can learn things with very few trials because we latchon to abstract relationships, whereas the machine requires many– perhaps thousands or millions – of examples to try tocatch extensionally what we get by the abstract or intensionalrelation. (ii) Deep learning is shallow and has a limited capacity fortransfer of what it has learnt from one context to another, eventhough the differences look trivial to us. It may follow thatcollecting examples cannot itself constitute ‘getting thepoint’, though it might manage to mimic it, if the circumstancesare carefully managed.

The dualist might sum up the situation on thought in the followingway. The case against physicalist theories of sensation is that it isunbelievable thatwhat it feels like to be struck hard on thenose is itself either just a case of being disposed or caused toengage in certain behaviours, or thatwhat it feels like isnot fundamental to the way you do react. Similarly, the dualist aboutthought will say, when you are, for example, engaged in aphilosophical discussion, and you make a response to yourinterlocutor, it is obvious that you are intending to respond towhat you thought he or she meant and are concentrating onwhatwhat you intend to say means. It seems as bizarre to saythat this is a byproduct of processes to which meaning is irrelevant,as it is to claim the same about sensory consciousness. You are, inother words, as fundamentally a semantically driven engine, as you area sensorily consciously driven one.

A dualist might, on this basis, argue that Plato was right in claimingthat intellect necessarily has an affinity with the realm of abstractentities, and Aristotle was right to think that no material ormechanical system could capture the flexibility built into genuineunderstanding.

4.5 The Argument from Predicate Dualism

We said above that predicate dualism might seem to have no ontologicalconsequences, because it is concerned only with the different waythings can be described within the contexts of the different sciences,not with any real difference in the things themselves. This, however,can be disputed.

The argument from predicate to property dualism moves in two steps,both controversial. The first claims that the irreducible specialsciences, which are the sources of irreducible predicates, are notwholly objective in the way that physics is, but depend for theirsubject matter upon interest-relative perspectives on the world. Thismeans that they, and the predicates special to them, depend on theexistence of minds and mental states, for only minds haveinterest-relative perspectives. The second claim is that psychology– the science of the mental – is itself an irreduciblespecial science, and so it, too, presupposes the existence of themental. Mental predicates therefore presuppose the mentality thatcreates them: mentality cannot consist simply in the applicability ofthe predicates themselves.

First, let us consider the claim that the special sciences are notfully objective, but are interest-relative.

No-one would deny, of course, that the very same subject matter or‘hunk of reality’ can be described in irreduciblydifferent ways and it still be just that subject matter or piece ofreality. A mass of matter could be characterized as a hurricane, or asa collection of chemical elements, or as mass of sub-atomic particles,and there be only the one mass of matter. But such differentexplanatory frameworks seem to presuppose different perspectives onthat subject matter.

This is where basic physics, and perhaps those sciences reducible tobasic physics, differ from irreducible special sciences. On a realistconstrual, the completed physics cuts physical reality up at itsultimate joints: any special science which is nomically strictlyreducible to physics also, in virtue of this reduction, it could beargued, cuts reality at its joints, but not at its minutest ones. Ifscientific realism is true, a completed physics will tell onehowthe world is, independently of any special interest or concern:it is just how the world is. It would seem that, by contrast, ascience which is not nomically reducible to physics does not take itslegitimation from the underlying reality in this direct way. Rather,such a science is formed from the collaboration between, on the onehand, objective similarities in the world and, on the other,perspectives and interests of those who devise the science. Theconcept of hurricane is brought to bear from the perspective ofcreatures concerned about the weather. Creatures totally indifferentto the weather would have no reason to take the real patterns ofphenomena that hurricanes share as constituting a single kind ofthing. With the irreducible special sciences, there is an issue ofsalience , which involves a subjective component: aselectionof phenomena with a certain teleology in mind is required before theirstructures or patterns are reified. The entities of metereology orbiology are, in this respect, rather like Gestalt phenomena.

Even accepting this, why might it be thought that the perspectivalityof the special sciences leads to a genuine property dualism in thephilosophy of mind? It might seem to do so for the following reason.Having a perspective on the world, perceptual or intellectual, is apsychological state. So the irreducible special sciences presupposethe existence of mind. If one is to avoid an ontological dualism, themind that has this perspective must be part of the physical reality onwhich it has its perspective. But psychology, it seems to be almostuniversally agreed, is one of those special sciences that is notreducible to physics, so if its subject matter is to be physical, ititself presupposes a perspective and, hence, the existence of a mindtosee matter as psychological. If this mind is physical andirreducible, it presupposes mind to see it as such. We seem to be in avicious circle or regress.

We can now understand the motivation for full-blown reduction. A truebasic physics represents the world as it is in itself, and if thespecial sciences were reducible, then the existence of theirontologies would make sense as expressions of the physical, not justas ways of seeing or interpreting it. They could be understood‘from the bottom up’, not from top down. Theirreducibility of the special sciences creates no problem for thedualist, who sees the explanatory endeavor of the physical sciences assomething carried on from a perspective conceptually outside of thephysical world. Nor need this worry a physicalist,if he canreduce psychology, for then he could understand ‘from the bottomup’ the acts (with their internal, intentional contents) whichcreated the irreducible ontologies of the other sciences. Butpsychology is one of the least likely of sciences to be reduced. Ifpsychology cannot be reduced, this line of reasoning leads to realemergence for mental acts and hence to a real dualism for theproperties those acts instantiate (Robinson 2003).

4.6 From Property Dualism to Substance Dualism

As we noted in section 2.4, there exists a received opinion in recentphilosophy of mind that property dualism is greatly preferable tosubstance dualism. Here, we consider one kind of argument thatsubstance dualism is in fact more defensible. The argument discussedbelow presses the case that the mind is a substance in the sense thatit is a unitary entity, not a Buddhist or Humean bundle. For anargument that dualists must accept that the mind is a substance in thesense that it is an independent entity, capable of existing by itself,see Weir (2021c; 2023).

Hume is generally understood to advance what is known as the‘bundle’ theory of the self (Treatise Book I,Part IV, section VI), according to which there are mental states, butno further subject or substance which possesses them. He famouslyexpresses his theory as follows.

…when I enter most intimately into what I callmyself,I always stumble on some particular perception or other, of heat orcold, light or shade,love or hatred, pain or pleasure. I can nevercatchmyself at any time without a perception, and can neverobserve any thing but the perception.

Nevertheless, in the Appendix of the same work he expresseddissatisfaction with this account. Somewhat surprisingly, it is notvery clear just what his worry was, but it is expressed asfollows:

In short there are two principles, which I cannot render consistent;nor is it in my power to renounce either of them, viz. that all ourdistinct perceptions are distinct existences, andthat the mindnever perceives any real connection between distinctexistences.

Berkeley had entertained a similar theory to the one found inHume’s main text in hisPhilosophical Commentaries,(Notebook A, paras 577–81), but later rejected it for the claimthat we could have anotion, though not anidea oftheself. Something resembling this Berkeleian view isanticipated by Nyaya responses to the Buddhist bundle theory of themind in antiquity. It is expressed in more modern terms by JohnFoster.

A natural response to Hume would be to say that, even if we cannotdetect ourselves apart from our perceptions (our consciousexperiences)we can at least detect ourselves in them … Surely Iam aware of [my experience], so to speak, from the inside – notas something presented, but as something which I have or as theexperiential state which I am in … and this is equivalent tosaying that I detect it by being aware of myself being visually aware.(Foster 1991, 215)

There is a clash of intuitions here between which it is difficult toarbitrate. There is an argument that is meant to favour the need for asubject, as claimed by Berkeley and Foster.

If the bundle theory were true, then it should be possible toidentify mental events independently of, or prior to, identifying theperson or mind to which they belong.
It is not possible to identify mental events in this way.
Therefore the bundle theory is false.

E. J. Lowe (1996) defends this argument and argues for (2) asfollows.

What is wrong with the [bundle] theory is that … itpresupposes, untenably, that an account of the identity conditions ofpsychological modes can be provided which need not rely on referenceto persons. But it emerges that the identity of any psychological modeturns on the identity of the person that possesses it. What thisimplies is that psychological modes are essentially modes of persons,and correspondingly that persons can be conceived of assubstances.

To say that, according to the bundle theory, the identity conditionsof individual mental states must be independent of the identity of theperson who possesses them, is to say that their identity isindependent of the bundle to which they belong. Hume certainly thoughtsomething like this, for he thought that an impression might‘float free’ from the mind to which it belonged, but it isnot obvious that a bundle theorist is forced to adopt this position.Perhaps the identity of a mental event is bound up with the complex towhich it belongs. That this is impossible certainly needs furtherargument.

Hume seems, however, in the main text to unconsciously make aconcession to the opposing view, namely the view that there must besomething more than the items in the bundle to make up a mind. Hesays:

The mind is a kind of theatre where several perceptions successivelymake their appearance; pass, re-pass, glide away and mingle in aninfinite variety of postures and situations.

Talk of the mind as a theatre is, of course, normally associated withthe Cartesian picture, and the invocation of any necessary medium,arena or even a field hypostasize some kind of entity which binds thedifferent contents together and without which they would not be asingle mind. Modern Humeans – such as Parfit (1971; 1984) orDainton (2008) – replace the theatre with a co-consciousnessrelation. So the bundle theorist is perhaps not as restricted as Humethought. The bundle consists of the objects of awarenessand theco-consciousness relation (or relations) that hold between them.The modern bundle theorist might say that it is the nexus ofco-consciousness relations that constitutes our sense of the subjectand of the act of awareness of the object. This involves abandoningthe second of Hume’s principles,that the mind can neverperceive any connection between distinct existences, because theco-consciousness relation is something of which we are aware.

5. Problems for Dualism

By far the most influential objection to dualism is the problem ofinteraction, which we have already discussed in section 3.3. In thissection we consider two other facets of dualism that worry critics.First, there is what one might term thequeerness of themental if conceived of as non-physical. Second there is the difficultyof giving an account of the unity of the mind. Important challengesnot covered here include providing a dualist account of embodiment andexplaining when immaterial minds arise in the gestation of individualorganisms and in the evolution of species.

5.1 The Queerness of the Mental

Physical objects and their properties are sometimes observable andsometimes not, but any physical object is equally accessible, inprinciple, to anyone. From the right location, we could all see thetree in the quad, and, though none of us can observe an electrondirectly, everyone is equally capable of detecting it in the same waysusing instruments. But the possessor of mental states seems tohave a privileged access to them that no-one else can share. Thatis why there is a widely recognised sceptical ‘problem of otherminds’, but no comparably well established ‘problem of myown mind’. This suggests to some philosophers that minds are notordinary occupants of physical space.

Physical objects are spatio-temporal, and bear spatio-temporal andcausal relations to each other. Mental states seem to have causalpowers, but they also possess the mysterious property ofintentionality – beingabout other things –including things like Zeus and the square root of minus one, which donot exist. No mere physical thing could be said to be, in a literalsense, ‘about’ something else. The nature of the mental isboth queer and elusive. In Ryle’s deliberately abusive phrase,the mind, as the dualist conceives of it, is a ‘ghost in amachine’. Ghosts are mysterious and unintelligible: machines arecomposed of identifiable parts and work on intelligible principles.Considerations of this kind motivate many philosophers to avoiddualism if possible.

Arguably, this contrast holds only if we stick to a Newtonian andcommon-sense view of the material, however. Think instead of energyand force-fields in a space-time that possesses none of the propertiesthat our senses seem to reveal: on this conception, we seem to be ableto attribute to matter nothing beyond an abstruse mathematicalstructure. Whilst the material world, because of itsmathematicalisation, forms a tighter abstract system than mind, thesensible properties that figure as the objects of mental states mayconstitute the only intelligible content for any concrete picture ofthe world that we can devise. So, perhaps the world within theexperiencing mind is, once one considers it properly, no more –or even less – queer than the world outside it.

5.2 The Unity of the Mind

Whether one believes that the mind is a substance or just a bundle ofproperties, the same challenge arises, which is to explain the natureof the unity of the immaterial mind. For the Cartesian, that meansexplaining how we should understand the notion of immaterialsubstance. For the Humean, the issue is to explain the nature of therelationship between the different elements in the bundle that bindsthem into one thing. Neither tradition has been notably successful inthis latter task: indeed, Hume, in the appendix to theTreatise, declared himself wholly mystified by the problem,rejecting his own initial solution (though quite why is not clear fromthe text).

5.2.1 Unity and Bundle Dualism

If the mind is only a bundle of properties, without a mental substanceto unite them, then an account is needed of what constitutes itsunity. The only route appears to be to postulate a primitive relationof co-consciousness in which the various elements stand to eachother.

There are two strategies which can be used to attack the bundletheory. One is to claim that our intuitions favour belief in a subjectand that the arguments presented in favour of the bundle alternativeare unsuccessful, so the intuition stands. The other is to try torefute the theory itself. Foster (1991, 212–9) takes the formerpath. This is not effective against someone who thinks thatmetaphysical economy gives a prima facie priority to bundle theories,on account of their avoiding mysterious substances.

The core objection to bundle theories (e.g. Armstrong 1968,21–3) is that, because it takes individual mental contents asits elements, such contents should be able to exist alone, as couldthe individual bricks from a house. Hume accepted this consequence,but most philosophers regard it as absurd. There could not be a mindthat consisted of a lone pain or red after-image, especially not ofone that had detached itself from the mind to which it had previouslybelonged. Therefore it makes more sense to think of mental contents asmodes of a subject.

Bundle theorists tend to take phenomenal contents as the primaryelements in their bundle. Thus the problem is how to relate, say, thevisual field to the auditory field, producing a ‘unity ofapperception’, that is, a total experience that seems to bepresented to a single subject. Seeing the problem in this way hasobvious Humean roots. This atomistic conception of the problem becomesless natural if one tries to accommodate other kinds of mentalactivity and contents. How are acts of conceptualising, attending toor willing with respect to, such perceptual contents to be conceived?These kinds of mental acts seem to be less naturally treated as atomicelements in a bundle, bound by a passive unity of apperception.William James (1890, vol. 1, 336–41) attempts to answer theseproblems. He claims to introspect in himself a ‘pulse ofthought’ for each present moment, which he calls ‘theThought’ and which is the ‘vehicle of the judgement ofidentity’ and the ‘vehicle of choice as well as ofcognition’. These ‘pulses’ are united over timebecause each ‘appropriates’ the past Thoughts and‘makes us say “as sure as I exist, those past facts werepart of myself”. James attributes to these Thoughts acts ofjudging, attending, willing etc, and this may seem incoherent in theabsence of a genuine subject. But there is also a tendency to treatmany if not all aspects of agency as mere awareness of bodily actionsor tendencies, which moves one back towards a more normal Humeanposition. Whether James’ position really improves onHume’s, or merely mystifies it, is still a moot point. (But seeSprigge (1993), 84–97, for an excellent, sympatheticdiscussion.)

5.2.2 Unity and Substance Dualism

The problem is to explain what kind of a thing an immaterial substanceis, such that its presence explains the unity of the mind. The answersgiven can be divided into three kinds.

(a) The ‘ectoplasm’ account: The view that immaterialsubstance is a kind of immaterial stuff. There are two problems withthis approach. First, in so far as this ‘ectoplasm’ hasany characterisation as a ‘stuff’ – that is, astructure of its own over and above the explicitly mental propertiesthat it sustains – it leaves it as much a mystery whythis kind of stuff should support unified consciousexperience as it is why ordinary matter should. Second, andconnectedly, it is not clear in what sense such stuff is immaterial,except in the sense that it cannot be integrated into the normalscientific account of the physical world. Why is it not just anaberrant kind of physical stuff? One answer to the latter questionwould be that the immaterial stuff is fundamentally mental andtherefore not physical in the sense relevant to physicalism (Wilson2006, 92, fn 1).

b) The ‘consciousness’ account: The view thatconsciousness is the substance. Account (a) allowed the immaterialsubstance to have a nature over and above the kinds of state we wouldregard as mental. The consciousness account does not. This isDescartes’ view. The most obvious objection to this theory isthat it does not allow the subject to exist when unconscious. Thisforces one to take one of four possible theories. One could claim (i)that we are conscious when we do not seem to be (which wasDescartes’ view): or (ii) that we exist intermittently, thoughare still the same thing (which is Swinburne’s theory, (1997,179)): or (iii) that each of us consists of a series of substances,changed at any break in consciousness, which pushes one towards aconstructivist account of identity through time and so towards thespirit of the bundle theory: or (iv) even more speculatively, that theself stands in such a relation to the normal time series that its owncontinued existence is not brought into question by its failure to bepresent in time at those moments when it is not conscious within thatseries (Robinson, forthcoming).

(c) The ‘no-analysis’ account: The view that it is amistake to present any analysis. This is Foster’s view, andVendler (1984) and Madell (1981) appear to have similar positions.Foster argues that even the ‘consciousness’ account is anattempt to explain what the immaterial self is ‘made of’which assimilates it too far towards a kind of physical substance. Inother words, Descartes has only half escaped from the‘ectoplasmic’ model. (He has half escaped because he doesnot attribute non-mental properties to the self, but he is stillcaptured by trying to explain what it is made of.)

Foster (1991) expresses it as follows:

…it seems to me that when I focus on myself introspectively, Iam not only aware of being in a certain mental condition; I am alsoaware, with the same kind of immediacy, of being a certain sort ofthing…
It will now be asked: ‘Well, what is this nature, this sortalattribute? Let’s have it specified!’ But such a demand ismisconceived. Of course, I can give it a verbal label: for instance, Ican call it ‘subjectness’ or ‘selfhood’. Butunless they are interpreted ‘ostensively’, by reference towhat is revealed by introspective awareness, such labels will notconvey anything over and above the nominal essence of the term‘basic subject’. In this respect, however, there is nodifference between this attribute, which constitutes thesubject’s essential nature, and the specific psychologicalattributes of his conscious life…
Admittedly, the feeling that there must be more to be said from aGod’s eye view dies hard. The reason is that, even when we haveacknowledged that basic subjects are wholly non-physical, we stilltend to approach the issue of their essential natures in the shadow ofthe physical paradigm. (Foster 1991, 243–5)

Bibliography

Adams, M. M., 1992, ‘The resurrection of the body accordingto three medieval Aristotelians: Thomas Aquinas, John Duns Scotus,William Ockham’,Philosophical Topics, 20(2):1–33.
Adamson, P., 2018,Philosophy in the Islamic World,Oxford: Oxford University Press.
Almog, J., 2001,What am I? Descartes and the Mind-BodyProblem, Oxford: Oxford University Press.
Alter, T. and Y. Nagasawa (eds.). 2015,Consciousness in thePhysical World: Perspectives on Russellian Monism, New York:Oxford University Press.
Aquinas, St Thomas,Summa Theologica, London: Washbourne,1912.
Aristotle,De Anima, D.W. Hamlyn (trans.), Oxford:Clarendon Press, 1993.
Armstrong, D. M., 1968,A Materialist Theory of the Mind,London: Routledge and Kegan Paul.
–––, 1978,Universals and Scientific Realism(2 vols), Cambridge: Cambridge University Press.
Ayer, A. J., 1963, ‘The concept of a person’, inThe Concept of a Person and other Essays, London: Macmillan,pp. 82–128.
Baker, M. C. 2011, ‘Brains and souls; grammar andspeaking’, in Baker, M. C. and S. Goetz (eds.), The SoulHypothesis, London: Continuum, pp. 73–93.
Benacerraf, P., 1983, ‘Mathematical Truth’, inBenacerraf and Putnam (eds.),Philosophy of Mathematics: SelectedReadings, Cambridge: Cambridge University Press, pp.403–420.
Benovsky, Jiri., 2009, ‘The self: A Humean bundle and/or aCartesian substance?’,European Journal of AnalyticPhilosophy, 5(2): 7–19.
Bering, J., & Bjorklund, D., 2004, ‘The naturalemergence of reasoning about the afterlife as a developmentalregularity’,Developmental Psychology, 40(2):217–233.
–––, 2006, ‘The folk psychology of souls’,The Behavioural and Brain Sciences, 29(5):453–532.
Berkeley, G., 1710,Principles of Human Knowledge in A.A.Luce and T.E. Jessop (eds.), The Works of George Berkeley, Bishop ofCloyne, Vol. 2, pp. 41–113, London: Thomas Nelson and Sons,1949.
Bloom, P., 2007, ‘Religion is natural’,Developmental Science, 10(1): 147–51.
Bourget, D. and D. Chalmers, 2023, ‘Philosophers onphilosophy’,Philosophers’ Imprint, 22:11.doi:10.3998/phimp.2109
Bricke, J., 1975, ‘Interaction and physiology’,Mind, 84: 255–9.
Broackes, J., 2006, ‘Substance.’Proceedings ofthe Aristotelian Society, 106(1): 133–68.doi:10.1111/j.1467-9264.2006.00142.x
Broad, C. D., 1925,The Mind and its Place in Nature,London: Routledge and Kegan Paul.
Brown, W. S., N. Murphy, and H. N. Malony. 1998,WhateverHappened to the Soul? Scientific and Theological Portraits of HumanNature, Minneapolis, MN: Fortress Press.
Cary, P., 2002,Augustine’s Invention of the Inner Self:The Legacy of a Christian Platonist, Oxford: Oxford UniversityPress.
Chalmers, D., 1996,The Conscious Mind: In Search of aFundamental Theory, New York: Oxford University Press.
–––, 2002, ‘Does Conceivability EntailPossibility?,’, in T. Gendler & J. Hawthorne(eds.),Conceivability and Possibility, Oxford: OxfordUniversity Press, pp. 145–200.
–––, 2010,The Character ofConsciousness, Oxford: Oxford University Press.
–––, 2018, ‘The meta-problem ofconsciousness’, Journal of Consciousness Studies,25(9–10): 6–61.
Cleeveley, H., 2022, ‘The a priori truth of modalrationalism’,The Philosophical Quarterly, 72(4):816–36. doi:10.1093/pq/pqab061
Collins, C., 1997, ‘Searle on consciousness anddualism’,International Journal of PhilosophicalStudies, 5: 15–33.
Collins, R., 2011, ‘Energy of the soul’, in M. C.Baker and S. Goetz,The Soul Hypothesis: Investigations into theExistence of the Soul, New York: Continuum International, pp.123–133.
Crane, T., 2003, ‘Mental substances’, in A.O’Hear (ed.), Minds and Persons, Cambridge: Cambridge UniversityPress, pp. 229–251.
Cross, R., 1998,The Physics of Duns Scotus: The ScientificContext of a Theological Vision, Oxford: Oxford UniversityPress.
Cucu, A., 2023, ‘Turning the tables: How neurosciencesupports interactive dualism’,Mind and Matter 21(2):219–2023.
Cucu, A. C. and J. B. Pitts, 2019, ‘How a dualist should(not) respond to the objection from energy conservation’,Mind and Matter, 17: 95–121.
Dainton, B., 2008,The Phenomenal Self, Oxford: OxfordUniversity Press.
Davidson, D., 1971, ‘Mental events’, in L. Foster andJ. W. Swanson (eds.),Experience and Theory, London:Duckworth, pp. 207–224.
De Haan, D. and B. Dahm, 2019, ‘Thomas Aquinas on separatedsouls as incomplete human persons’,The Thomist, 83(4):589–637.
Dennett, D., 1987, ‘Three kinds of intentionalpsychology’, inThe Intentional Stance, Cambridge, MA:MIT Press, pp. 43–68.
–––, 1984, ‘Cognitive wheels: the frameproblem of AI’, in C. Hookway (ed.),Minds, Machines andEvolution, Cambridge: Cambridge University Press, pp.129–152.
–––, 1991,Consciousness Explained,Boston, MA: Little Brown & Co.
Descartes, R.The Philosophical Writings of Descartes, J.Cottingham, R. Stoothoff, D. Murdoch, and A. Kenny (eds. and trans.),Cambridge: Cambridge University Press, 1984–91.
Ducasse, C., 1961, ‘In defence of dualism’, in S. Hook(ed.),Dimensions of Mind, New York: Collier, pp.85–9.
Easwaran, E. (trans.), 2007,The Bhagavad Gita, TomalesCA: Nilgiri Press.
Eccles, J, 1987, ‘Brain and mind: two or one?’ in C.Blakemore and S. Green fields (eds.),Mindwaves, Oxford:Blackwell, pp. 293–306.
–––, 1980,The Human Psyche, New York:Springer.
–––, 1994,How the Self Controls itsBrain, Berlin: Springer.
Efron, A., 1992, ‘Residual asymmetric dualism: a theory ofmind-body relations’,Journal of Mind and Behaviour,13: 113–36.
Epicurus, ‘Letter to Herodotus’, in Brad Inwood and L.P. Gearson (eds. and trans.),Hellenistic Philosophy: IntroductoryReadings, Indianapolis: Hackett, 1997, pp. 5–19.
Farris, J. and J. Leidenhag, 2024,The Origin of the Soul: AConversation, New York: Routledge.
Feigl, H., 1958, ‘The “mental” and the“physical”’, in H. Feigl, M. Scriven and G. Maxwell,(eds.),Concepts, Theories and the Mind-Body Problem(Minnesota Studies in the Philosophy of Science, Volume 2),Minneapolis: Minnesota University Press, pp. 370–497.
Feser, E., 2006,Philosophy of Mind: A Beginner’s Guide,Oxford: Oneworld Publications.
–––, 2013, ‘Kripke, Ross, and theimmaterial aspects of thought’,American CatholicPhilosophical Quarterly 87: 1–32.
–––, 2024, Immortal Souls: A Treatise on HumanNature, Neunkirchen-Seelscheid: Editiones Scholasticae.
Fodor, J., 1974, ‘Special sciences and the disunity ofscience as a working hypothesis’,Synthese, 28:77–115.
–––, 2000,The Mind Does Not Work ThatWay, Cambridge MA: MIT Press.
Foster, J., 1968, ‘Psycho-physical causal relations’,American Philosophical Quarterly, 5: 64–70.
–––, 1989, ‘A defence of dualism’,in J. Smythies and J. Beloff (eds.),The Case for Dualism,Charlottesville: University of Virginia Press, pp. 59–80.
–––, 1991,The Immaterial Self, London:Routledge.
Francescotti, R., 2001, ‘Property Dualism without SubstanceDualism?’,Philosophical Papers, 30(2):93–116.
Freeman, A. (ed.), 2006,Consciousness and its Place inNature: Does Physicalism Entail Panpsychism?, Exeter: ImprintAcademic.
Fumerton, R., 2013,Knowledge, Thought and the Case forDualism, Cambridge: Cambridge University Press.
Goetz, S., 2016, ‘Free will and substance dualism’, inK. Timpe, M. Griffith and N. Levy (eds.)The Routledge Companionto Free Will, New York: Routledge.
Goff, P., 2017,Consciousness and Fundamental Reality,Oxford: Oxford University Press.
Goff, P. and A. Moran (eds.), 2022,Is ConsciousnessEverywhere? Essays on Panpsychism, Exeter: Imprint Academic.
Gopnik, A., 2009, ‘Could David Hume have known aboutBuddhism? Charles François Dolu, the Royal College of LaFlèche, and the global Jesuit intellectual network’,Hume Studies, 35(1–2): 5–28.
Green, C., 2003,The Lost Cause, Oxford: OxfordForum.
Hamlyn, D. W., 1978, ‘Aristotle’s Cartesianism’,Paedia, 2nd special issue (Aristotle): 8–15.
Hart, W. D., 1994, ‘Dualism’, in S. Guttenplan (ed.),A Companion to the Philosophy of Mind, Oxford: Blackwell, pp.265–7.
–––, 1988,Engines of the Soul,Cambridge: Cambridge University Press.
Hasker, W., 1999,The Emergent Self, Ithaca, NY: CornellUniversity Press.
Hawthorne, J., 2007, ‘Cartesian dualism’, in P. vanInwagen and D. Zimmerman (eds.),Persons Human and Divine,Oxford: Oxford University Press, pp. 87–98.
Heil, J., 1998,Philosophy of Mind, London and New York:Routledge.
Herbert, R. T., 1998, ‘Dualism/materialism’,Philosophical Quarterly, 48: 159–75.
Himma, K. E., 2005, ‘When a problem for all is a problem fornone: substance dualism, physicalism and the mind-body problem’,American Philosophical Quarterly, 42: 81–92.
Hodge, K. M., 2008, ‘Descartes’ mistake: how afterlife beliefschallenge the assumption that humans are intuitive cartesian substancedualists’,Journal of Cognition and Culture, 8:387–415.
Hodgson, D., 1988,The Mind Matters: Consciousness and Choicein a Quantum World, Oxford: Oxford University Press.
Honderich, T., 1981, ‘Psychophysical law-like connectionsand their problems’,Inquiry, 24: 277–303.
Hume, D., 1739,A Treatise of Human Nature, Bk I, Pt IV,sect. VI, and Appendix, D.F. Norton and M.J. Norton (eds.), Oxford:Oxford University Press, 2000.
Huxley, T. H., 1893, ‘On the hypothesis that animals areautomata’, inCollected Essays (Volume 1), London:Macmillan, pp. 199–250.
Jackson, F., 1982, ‘Epiphenomenal qualia’,Philosophical Quarterly, 32: 127–136.
–––, 2003, ‘Mind and Illusion’, inAnthony O’Hear (ed.)Minds and Persons, Cambridge:Cambridge University Press.
James, W., 1890,Principles of Psychology, London:Macmillan.
Kenny, A., 1989,The Metaphysics of Mind, Oxford:Clarendon Press.
Kim, J., 2003, ‘Lonely souls: causality and substancedualism’, in T. O’Connor and D. Robb (eds.),Philosophy of Mind: Contemporary Readings, London: Routledge,pp. 65–78..
Kitzler, P., 2015, ‘Tertullian’s concept of the souland his corporealistic ontology’, in J. Lagouanère and S.Fialon (eds.),Tertullianus Afer: Tertullien et lalittérature chrétienne d’Afrique, Turnhout: BrepolsPublishers, 43–62. doi:10.1484/M.IPM-EB.4.00004
Kripke, S., 1972/1980,Naming and Necessity, Oxford:Blackwell.
–––, 1982,Wittgenstein on Rules and PrivateLanguage, Cambridge MA: Harvard.
Kuhn, R. L., 2024, ‘A landscape of consciousness: Toward ataxonomy of explanations and implications’,Progress in Biophysicsand Molecular Biology, 190: 28—168.
Lahav, R. and N. Shanks, 1982, ‘How to be a scientificallyrespectable “property dualist”’,Journal of Mindand Behaviour, 13: 211–32.
Larmer, R., 1986, ‘Mind-body interactionism and theconservation of energy’,International PhilosophicalQuarterly, 26: 277–85.
Latham, N., 2000, ‘Chalmers on the addition of consciousnessto the physical world’,Philosophical Studies, 98:67–93.
Lowe, E. J., 1992, ‘The problem of psychophysicalcausation’,Australasian Journal of Philosophy, 70:263–76.
–––, 1993, ‘The causal autonomy of themental’,Mind, 102: 629–44.
–––, 1996,Subjects of Experience,Cambridge: Cambridge University Press.
–––, 2006, ‘Non-Cartesian substancedualism and the problem of mentalcausation’,Erkenntnis, 65(1): 5–23.
Lycan, W., 2013, ‘Is property dualism better off thansubstance dualism?’,Philosophical Studies, 164(2):533–42.
Madell, G., 1981,The Identity of the Self, Edinburgh:Edinburgh University Press.
–––, 2010, ‘The road to substancedualism’,Royal Institute of Philosophy Supplements, 67: 45–60.doi:10.1017/S1358246110000111
Markie, P., 1994. ‘Descartes’ conception ofsubstance’, in J. Cottingham (ed.), Reason, Will and Sensation:Studies in Descartes’ Metaphysics, Oxford: Oxford UniversityPress.
McGinn, C., 1993, ‘Consciousness and cosmology: hyperdualismventilated’, in M. Davies and G. Humphreys (eds.),Consciousness: Psychological and Philosophical Essays,Oxford: Blackwell, pp. 136–168.
Mills, E., 1996, ‘Interaction and overdetermination’,American Philosophical Quarterly, 33: 105–15.
Nagel, E., 1961.The Structure of Science: Problems in theLogic of Explanation, New York: Harcourt Brace & World.
Nida-Rümelin, M., 2012, ‘The conceptual origin ofsubject body dualism’, in A. Colliva (ed.),Self andSelf-Knowledge, Oxford: Oxford University Press.
Nussbaum, M. C., 1984, ‘Aristotelian dualism’,Oxford Studies in Ancient Philosophy, 2: 197–207.
Nussbaum, M. C. and A. O. Rorty, 1992,Essays onAristotle’s De Anima, Oxford: Clarendon Press.
Oderberg, D. S., 2005, ‘Hylemorphic dualism’,Social Philosophy and Policy, 22: 70–99.
O’Hear, A., 2025,Popper, Philosophy and Faith,Cambridge: Cambridge University Press.
Olivelle, P. (trans. and ed.), 1998,The Early Upanishads,Annotated Text and Translation, Oxford: Oxford UniversityPress.
O’Leary-Hawthorne, J. and J. K. McDonough, 1998,‘Numbers, minds and bodies: a fresh look at mind-bodydualism’,Philosophical Perspectives, 12:349–71.
Papineau, D., 2001, ‘The rise of physicalism’, in C.Gillett & B. Loewer,Physicalism and its Discontents,Cambridge: Cambridge University Press, 3–36.
Parfit, D., 1971, ‘Personal identity’,Philosophical Review, 80: 3–27.
–––, 1984,Reasons and Persons, Oxford:Clarendon Press.
Pearson, O., 2018,Rationality, Time, and Self, Berlin:Springer.
Penelhum, T., 1970,Survival and Disembodied Existence,London: Routledge and Kegan Paul.
Penfield, W., 1975,The Mystery of the Mind: A Critical Studyof Consciousness and the Human Brain, Princeton, NJ: PrincetonUniversity Press.
Penrose, R., 1990,The Emperor’s New Mind, Oxford:Oxford University Press.
Pessin, S., 2013,Ibn Gabirol’s Theology of Desire:Matter and Method in Jewish Medieval Neoplatonism, Cambridge:Cambridge University Press.
Pietroski, P. M., 1994, ‘Mental causation fordualists’,Mind and Language, 9: 336–66.
Pitts, J. B., 2019, ‘Conservation laws and the philosophy ofmind: opening the black box, finding a mirror’,Philosophia, 48: 673–707.
Plato,Complete Works, J. Cooper (ed.), Indianapolis:Hackett, 1997.
Popper, K., 1963,Conjectures and Refutations: The Growth ofScientific Knowledge, London: Routledge and Kegan Paul.
Popper, K. and J. Eccles, 1977,The Self and its Brain,New York: Springer.
Radhakrishnan, S., and C. A. Moore, 1958,A Sourcebook inIndian Philosophy, Princeton, NJ: Princeton UniversityPress.
Reid, T., 1785, ‘Of Memory’, inEssays on theIntellectual Powers of Man, Cambridge, MA: MIT Press, 1969, pp.211–253.
Richardson, R. C., 1982, ‘The ‘scandal’ ofCartesian dualism’,Mind, 91: 20–37.
Robinson, H., 1982,Matter and Sense, Cambridge:Cambridge University Press.
–––, 1983, ‘Aristoteliandualism’,Oxford Studies in Ancient Philosophy, 1:123–44.
–––, 2003, ‘Dualism’, in S. Stichand T. Warfield (eds.),The Blackwell Guide to Philosophy ofMind, Oxford: Blackwell, pp. 85–101.
–––, 2007, ‘The self and time’, inP. van Inwagen and D. Zimmerman (eds.),Persons, Human andDivine, Oxford: Oxford University Press, pp. 55–83.
–––, 2011, ‘Benacerraf’s problem,abstract objects and intellect’, in Z. Novak and A. Simony(eds.),Truth, Reference and Realism, Budapest: CEU Press, pp.235–62.
–––, 2016,From Knowledge Argument to MentalSubstance: Resurrecting the Mind, Cambridge: Cambridge UniversityPress.
–––, 2022,Perception and Idealism: An Essayon How the World Manifests Itself to Us, and How It (Probably) Is inItself, Oxford: Oxford University Press.
Rosenburg, J. F., 1988, ‘On not knowing who or what one is:reflections on the intelligibility of dualism’,Topoi,7: 57–63.
Ross, J., 2008,Thought and World: The HiddenNecessities, Notre Dame, IN: University of Notre Dame Press.
Rozemond, M., 2002,Descartes’s Dualism, Cambridge,MA: Harvard University Press.
Ryle, G., 1949,The Concept of Mind, London:Hutchinson.
Schneider, S., 2012, ‘Why property dualists must rejectsubstance physicalism’,Philosophical Studies, 157:61–76.
Schweizer, P., 2019, ‘Sāṃkhya-Yoga philosophy andthe mind-body problem’, Prabuddha Bharata or Awakened India,124(1), 232–242.
Searle, J., 1980, ‘Minds, brains and programs’,Behavioural and Brain Science, 3: 417–457.
–––, 2002, ‘Why I am not a propertydualist’,Journal of Consciousness Studies, 9(12): 57–64.
Sellars, W., 1954, ‘A note on Popper’s argument fordualism’,Analysis, 15: 23–4.
Sherrington, C. S., 1951,Man on his Nature (2nd ed.),Cambridge: Cambridge University Press.
Shoemaker, S., 1984,Identity, Cause, and Mind,Cambridge: Cambridge University Press.
Skrezypek, J., 2021, ‘Not just a terminological difference:Cartesian substance dualism vs Thomistic hylomorphism’,Roczniki Filozoficzne, 69(1): 103–118.
Slingerland, E., 2013, ‘Body and mind in early China: anintegrated humanities-science approach.’Journal of theAmerican Academy of Religion, 81(1): 6–55.
Smook, R., 1988, ‘Egoicity and Twins’,Dialogue, 27: 277–86.
Smythies, J. R. and J. Beloff (eds.), 1989,The Case forDualism, Charlottesville: University of Virginia Press.
Sprigge, T. L. S., 1994, ‘Consciousness’,Synthese, 98: 73–93.
–––, 1993,James and Bradley: American Truthand British Reality, Chicago: Open Court.
Stapp, H. P., 1993,Mind, Matter, and Quantum Mechanics,Berlin: Springer-Verlag.
Steadman, L., C. Palmer, and C. Tiller, 1996, ‘Theuniversality of ancestor worship’,Ethnology, 35(1):63–76.
Strawson, P. F., 1959,Individuals, London: Methuen.
Sussman, A., 1981, ‘Reflections on the chances for ascientific dualism’,Journal of Philosophy, 78:95–118.
Swinburne, R., 1986,The Evolution of the Soul, Oxford:Clarendon Press; revised edition, 1997.
–––, 2007, ‘From mental/physical identityto substance dualism’, in P. van Inwagen and D. Zimmerman(eds.),Persons Human and Divine, Oxford: Oxford University Press,pp. 142–65.
–––, 2013,Mind, Brain and Free Will,Oxford: Oxford University Press.
–––, 2014, ‘What makes me, me? A defenseof substance dualism’, in A. Lavazzo and H. Robinson (eds.),Contemporary Dualism: a Defense, London: Routledge,139–53.
–––, 2018, ‘Cartesian substancedualism’, in J. Loose, A. Menuge, and J. P. Moreland(eds.),The Blackwell Companion to Substance Dualism, Oxford:Blackwell.
–––, 2019,Are We Bodies or Souls?Oxford: Oxford University Press.
Taliaferro, C., 1996,Consciousness and the Mind of God,Cambridge: Cambridge University Press.
–––, 2018, ‘Substance dualism: adefense’, in J. Loose, A. Menuge, and J. P. Moreland(eds.),The Blackwell Companion to Substance Dualism, Oxford:Blackwell.
Van Inwagen, Peter and Dean Zimmerman, 2007,Persons: Humanand Divine, Oxford: Oxford University Press.
Vendler, Z., 1984,The Matter of Minds, Oxford: ClarendonPress.
–––, 1972,Res Cogitans, Ithaca, NY:Cornell University Press.
Von Rooijen, K., 1987, ‘Interactionism and evolution: acritique of Popper’,British Journal for the Philosophy ofScience, 38: 87–92.
Von Wright, G. H., 1994, ‘On mind and matter’,Journal of Theoretical Biology, 171: 101–10.
Watson, J. B., 1913, ‘Psychology as the behaviourist viewsit’,Psychological Review, 20: 158–77.
Weir, R. S., 2021a, ‘Bring back substances!’,TheReview of Metaphysics, 75(2): 265–308.doi:10.1353/rvm.2021.0040
–––, 2021b, ‘Does idealism solve theproblem of consciousness?’, in J. Farris and B. Göcke(eds.),The Routledge Handbook for Idealism andImmaterialism, New York: Routledge.
–––, 2021c, ‘Can a post-Galilean scienceof consciousness avoid substance dualism?’,Journal ofConsciousness Studies, 28(9–10): 212–28.
–––, 2022, ‘Christian physicalism and thebiblical argument for dualism’,International Journal forPhilosophy of Religion, 91: 115–138.
–––, 2023,The Mind-Body Problem andMetaphysics, New York: Routledge.
Wilson, J., 2006, ‘On Characterising the Physical’,Philosophical Studies, 131: 61–99.doi:10.1007/s11098-006-5984-8
Wolff, C., 1751,Vernünfftige Gedancken von Gott, derWelt und der Seele des Menschen, auch allen Dingen überhaupt, denLiebhabern der Wahrheit mit-getheilet, Halle: Renger.
Zimmerman, D., 2004, ‘Should a Christian be a mind-bodydualist?’, inContemporary Debates in Philosophy ofReligion, Malden, MA: Blackwell, pp. 341–352.
–––, 2010, ‘From property dualism tosubstance dualism’,Proceedings of the AristotelianSociety (Supplementary Volume), 84(1): 119–50.
Zongmi, G., 2014, ‘On humanity’, (extracts), in J. Tiwaldand B. W. Van Norden (eds.) Readings in Later Chinese Philosophy: HanDynasty China to the 20th Century, Cambridge: Hackett, 98–106.

Academic Tools

How to cite this entry.
Preview the PDF version of this entry at theFriends of the SEP Society.
Look up topics and thinkers related to this entry at the Internet Philosophy Ontology Project (InPhO).
Enhanced bibliography for this entryatPhilPapers, with links to its database.

Other Internet Resources

Marcus, G., 2018, ‘Deep learning: a critical appraisal’, arXiv:1801.00631
Papers on Materialism and Dualism, at philpapers.org.
Mind and body, René Descartes to William James, by Robert H. Wozniak, Bryn Mawr.

Open access to the SEP is made possible by a world-wide funding initiative.
The Encyclopedia Now Needs Your Support
Please Read How You Can Help Keep the Encyclopedia Free

Browse

About

Support SEP

Mirror Sites

View this site from another server:

USA (Main Site)Philosophy, Stanford University

Info about mirror sites

Library of Congress Catalog Data: ISSN 1095-5054

Movatterモバイル変換