In philosophy, physicalism is the metaphysical thesis that "everything is physical", that there is "nothing over and above" the physical,[1] or that everything supervenes on the physical.[2] Physicalism is a form of ontological monism—a "one substance" view of the nature of reality as opposed to a "two-substance" (dualism) or "many-substance" (pluralism) view. Both the definition of "physical" and the meaning of physicalism have been debated.

Physicalism is closely related to materialism. Physicalism grew out of materialism with advancements of the physical sciences in explaining observed phenomena. The terms are often used interchangeably, although they are sometimes distinguished, for example on the basis of physics describing more than just matter (including energy and physical law). Common arguments against physicalism include both the philosophical zombie argument[3] and the multiple observers argument,[4] that the existence of a physical being may imply zero or more distinct conscious entities.

Definition of physicalism

The word "physicalism" was introduced into philosophy in the 1930s by Otto Neurath and Rudolf Carnap.[5]

The use of "physical" in physicalism is a philosophical concept and can be distinguished from alternative definitions found in the literature (e.g. Karl Popper defined a physical proposition to be one which can at least in theory be denied by observation[6]). A "physical property", in this context, may be a metaphysical or logical combination of properties which are physical in the ordinary sense. It is common to express the notion of "metaphysical or logical combination of properties" using the notion of supervenience: A property A is said to supervene on a property B if any change in A necessarily implies a change in B.[7] Since any change in a combination of properties must consist of a change in at least one component property, we see that the combination does indeed supervene on the individual properties. The point of this extension is that physicalists usually suppose the existence of various abstract concepts which are non-physical in the ordinary sense of the word; so physicalism cannot be defined in a way that denies the existence of these abstractions. Also, physicalism defined in terms of supervenience does not entail that all properties in the actual world are type identical to physical properties. It is, therefore, compatible with multiple realizability.[8]

From the notion of supervenience, we see that, assuming that mental, social, and biological properties supervene on physical properties, it follows that two hypothetical worlds cannot be identical in their physical properties but differ in their mental, social or biological properties.[2]

Two common approaches to defining "physicalism" are the theory-based and object-based approaches. The theory-based conception of physicalism proposes that "a property is physical if and only if it either is the sort of property that physical theory tells us about or else is a property which metaphysically (or logically) supervenes on the sort of property that physical theory tells us about".[2] Likewise, the object-based conception claims that "a property is physical if and only if: it either is the sort of property required by a complete account of the intrinsic nature of paradigmatic physical objects and their constituents or else is a property which metaphysically (or logically) supervenes on the sort of property required by a complete account of the intrinsic nature of paradigmatic physical objects and their constituents".

Physicalists have traditionally opted for a "theory-based" characterization of the physical either in terms of current physics,[9] or a future (ideal) physics.[10] These two theory-based conceptions of the physical represent both horns of Hempel's dilemma[11] (named after the late philosopher of science and logical empiricist Carl Gustav Hempel): an argument against theory-based understandings of the physical. Very roughly, Hempel's dilemma is that if we define the physical by reference to current physics, then physicalism is very likely to be false, as it is very likely (by pessimistic meta-induction[12]) that much of current physics is false. But if we instead define the physical in terms of a future (ideal) or completed physics, then physicalism is hopelessly vague or indeterminate.[13]

While the force of Hempel's dilemma against theory-based conceptions of the physical remains contested,[14] alternative "non-theory-based" conceptions of the physical have also been proposed. Frank Jackson (1998) for example, has argued in favour of the aforementioned "object-based" conception of the physical.[15] An objection to this proposal, which Jackson himself noted in 1998, is that if it turns out that panpsychism or panprotopsychism is true, then such a non-materialist understanding of the physical gives the counterintuitive result that physicalism is, nevertheless, also true since such properties will figure in a complete account of paradigmatic examples of the physical.

David Papineau[16] and Barbara Montero[17] have advanced and subsequently defended[18] a "via negativa" characterization of the physical. The gist of the via negativa strategy is to understand the physical in terms of what it is not: the mental. In other words, the via negativa strategy understands the physical as "the non-mental". An objection to the via negativa conception of the physical is that (like the object-based conception) it doesn't have the resources to distinguish neutral monism (or panprotopsychism) from physicalism.[19]

Supervenience-based definitions of physicalism

Adopting a supervenience-based account of the physical, the definition of physicalism as "all properties are physical" can be unravelled to:

1) Physicalism is true at a possible world w if and only if any world that is a physical duplicate of w is also a duplicate of w simpliciter.[20]

Applied to the actual world (our world), statement 1 above is the claim that physicalism is true at the actual world if and only if at every possible world in which the physical properties and laws of the actual world are instantiated, the non-physical (in the ordinary sense of the word) properties of the actual world are instantiated as well. To borrow a metaphor from Saul Kripke (1972), the truth of physicalism at the actual world entails that once God has instantiated or "fixed" the physical properties and laws of our world, then God's work is done; the rest comes "automatically".

Unfortunately, statement 1 fails to capture even a necessary condition for physicalism to be true at a world w. To see this, imagine a world in which there are only physical properties—if physicalism is true at any world it is true at this one. But one can conceive physical duplicates of such a world that are not also duplicates simpliciter of it: worlds that have the same physical properties as our imagined one, but with some additional property or properties. A world might contain "epiphenomenal ectoplasm", some additional pure experience that does not interact with the physical components of the world and is not necessitated by them (does not supervene on them).[21][22] To handle the epiphenomenal ectoplasm problem, statement 1 can be modified to include a "that's-all" or "totality" clause[23] or be restricted to "positive" properties.[24] Adopting the former suggestion here, we can reformulate statement 1 as follows:

2) Physicalism is true at a possible world w if and only if any world that is a minimal physical duplicate of w is a duplicate of w simpliciter.[20]

Applied in the same way, statement 2 is the claim that physicalism is true at a possible world w if and only if any world that is a physical duplicate of w (without any further changes), is duplicate of w without qualification. This allows a world in which there are only physical properties to be counted as one at which physicalism is true, since worlds in which there is some extra stuff are not "minimal" physical duplicates of such a world, nor are they minimal physical duplicates of worlds that contain some non-physical properties that are metaphysically necessitated by the physical.[25]

But while statement 2 overcomes the problem of worlds at which there is some extra stuff (sometimes referred to as the "epiphenomenal ectoplasm problem"[26]) it faces a different challenge: the so-called "blockers problem".[27] Imagine a world where the relation between the physical and non-physical properties at this world (call the world w1) is slightly weaker than metaphysical necessitation, such that a certain kind of non-physical intervener—"a blocker"—could, were it to exist at w1, prevent the non-physical properties in w1 from being instantiated by the instantiation of the physical properties at w1. Since statement 2 rules out worlds which are physical duplicates of w1 that also contain non-physical interveners by virtue of the minimality, or that's-all clause, statement 2 gives the (allegedly) incorrect result that physicalism is true at w1. One response to this problem is to abandon statement 2 in favour of the alternative possibility mentioned earlier in which supervenience-based formulations of physicalism are restricted to what David Chalmers (1996) calls "positive properties". A positive property is one that "...if instantiated in a world W, is also instantiated by the corresponding individual in all worlds that contain W as a proper part."[28] Following this suggestion, we can then formulate physicalism as follows:

3) Physicalism is true at a possible world w if and only if any world that is a physical duplicate of w is a positive duplicate of w.[29]

On the face of it, statement 3 seems able to handle both the epiphenomenal ectoplasm problem and the blockers problem. With regard to the former, statement 3 gives the correct result that a purely physical world is one at which physicalism is true, since worlds in which there is some extra stuff are positive duplicates of a purely physical world. With regard to the latter, statement 3 appears to have the consequence that worlds in which there are blockers are worlds where positive non-physical properties of w1 will be absent, hence w1 will not be counted as a world at which physicalim is true.[30] Daniel Stoljar (2010) objects to this response to the blockers problem on the basis that since the non-physical properties of w1 aren't instantiated at a world in which there is a blocker, they are not positive properties in Chalmers' (1996) sense, and so statement 3 will count w1 as a world at which physicalism is true after all.[31]

A further problem for supervenience-based formulations of physicalism is the so-called "necessary beings problem".[20] A necessary being in this context is a non-physical being that exists in all possible worlds (for example what theists refer to as God). A necessary being is compatible with all the definitions provided, because it is supervenient on everything; yet it is usually taken to contradict the notion that everything is physical. So any supervenience-based formulation of physicalism will at best state a necessary but not sufficient condition for the truth of physicalism.[20]

Additional objections have been raised to the above definitions provided for supervenience physicalism: one could imagine an alternate world that differs only by the presence of a single ammonium molecule (or physical property), and yet based on statement 1, such a world might be completely different in terms of its distribution of mental properties.[32] Furthermore, there are differences expressed concerning the modal status of physicalism; whether it is a necessary truth, or is only true in a world which conforms to certain conditions (i.e. those of physicalism).[2]

Realisation physicalism

Closely related to supervenience physicalism, is realisation physicalism, the thesis that every instantiated property is either physical or realised by a physical property.[33]

Token physicalism

Token physicalism is the proposition that "for every actual particular (object, event or process) x, there is some physical particular y such that x = y". It is intended to capture the idea of "physical mechanisms".[2] Token physicalism is compatible with property dualism, in which all substances are "physical", but physical objects may have mental properties as well as physical properties. Token physicalism is not however equivalent to supervenience physicalism. Firstly, token physicalism does not imply supervenience physicalism because the former does not rule out the possibility of non-supervenient properties (provided that they are associated only with physical particulars). Secondarily, supervenience physicalism does not imply token physicalism, for the former allows supervenient objects (such as a "nation", or "soul") that are not equal to any physical object.

Reductionism and emergentism


There are multiple versions of reductionism.[2] In the context of physicalism, the reductions referred to are of a "linguistic" nature, allowing discussions of, say, mental phenomena to be translated into discussions of physics. In one formulation, every concept is analysed in terms of a physical concept. One counter-argument to this supposes there may be an additional class of expressions which is non-physical but which increases the expressive power of a theory.[34] Another version of reductionism is based on the requirement that one theory (mental or physical) be logically derivable from a second.[35]

The combination of reductionism and physicalism is usually called reductive physicalism in the philosophy of mind. The opposite view is non-reductive physicalism. Reductive physicalism is the view that mental states are both nothing over and above physical states and reducible to physical states. One version of reductive physicalism is type physicalism or mind-body identity theory. Type physicalism asserts that "for every actually instantiated property F, there is some physical property G such that F=G".[2] Unlike token physicalism, type physicalism entails supervenience physicalism.

A common argument against type physicalism is multiple realizability, the possibility that a psychological process (say) could be instantiated by many different neurological processes (even non-neurological processes, in the case of machine or alien intelligence).[32][36] For in this case, the neurological terms translating a psychological term must be disjunctions over the possible instantiations, and it is argued that no physical law can use these disjunctions as terms.[36] Type physicalism was the original target of the multiple realizability argument, and it is not clear that token physicalism is susceptible to objections from multiple realizability.[37]


There are two versions of emergentism, the strong version and the weak version. Supervenience physicalism has been seen as a strong version of emergentism, in which the subject's psychological experience is considered genuinely novel.[2] Non-reductive physicalism, on the other side, is a weak version of emergentism because it does not need that the subject's psychological experience be novel. The strong version of emergentism is incompatible with physicalism. Since there are novel mental states, mental states are not nothing over and above physical states. However, the weak version of emergentism is compatible with physicalism.

We can see that emergentism is actually a very broad view. Some forms of emergentism appear either incompatible with physicalism or equivalent to it (e.g. posteriori physicalism),[38] others appear to merge both dualism and supervenience. Emergentism compatible with dualism claims that mental states and physical states are metaphysically distinct while maintaining the supervenience of mental states on physical states. This proposition however contradicts supervenience physicalism, which asserts a denial of dualism.

A priori versus a posteriori physicalism

Physicalists hold that physicalism is true. A natural question for physicalists, then, is whether the truth of physicalism is deducible a priori from the nature of the physical world (i.e., the inference is justified independently of experience, even though the nature of the physical world can itself only be determined through experience) or can only be deduced a posteriori (i.e., the justification of the inference itself is dependent upon experience). So-called "a priori physicalists" hold that from knowledge of the conjunction of all physical truths, a totality or that's-all truth (to rule out non-physical epiphenomena, and enforce the closure of the physical world), and some primitive indexical truths such as "I am A" and "now is B", the truth of physicalism is knowable a priori.[39] Let "P" stand for the conjunction of all physical truths and laws, "T" for a that's-all truth, "I" for the indexical "centering" truths, and "N" for any [presumably non-physical] truth at the actual world. We can then, using the material conditional "→", represent a priori physicalism as the thesis that PTI → N is knowable a priori.[39] An important wrinkle here is that the concepts in N must be possessed non-deferentially in order for PTI → N to be knowable a priori. The suggestion, then, is that possession of the concepts in the consequent, plus the empirical information in the antecedent is sufficient for the consequent to be knowable a priori.

An "a posteriori physicalist", on the other hand, will reject the claim that PTI → N is knowable a priori. Rather, they would hold that the inference from PTI to N is justified by metaphysical considerations that in turn can be derived from experience. So the claim then is that "PTI and not N" is metaphysically impossible.

One commonly issued challenge to a priori physicalism and to physicalism in general is the "conceivability argument", or zombie argument.[40] At a rough approximation, the conceivability argument runs as follows:

P1) PTI and not Q (where "Q" stands for the conjunction of all truths about consciousness, or some "generic" truth about someone being "phenomenally" conscious [i.e., there is "something it is like"[41] to be a person x] ) is conceivable (i.e., it is not knowable a priori that PTI and not Q is false).

P2) If PTI and not Q is conceivable, then PTI and not Q is metaphysically possible.

P3) If PTI and not Q is metaphysically possible then physicalism is false.

C) Physicalism is false.[42]

Here proposition P3 is a direct application of the supervenience of consciousness, and hence of any supervenience-based version of physicalism: If PTI and not Q is possible, there is some possible world where it is true. This world differs from [the relevant indexing on] our world, where PTIQ is true. But the other world is a minimal physical duplicate of our world, because PT is true there. So there is a possible world which is a minimal physical duplicate of our world, but not a full duplicate; this contradicts the definition of physicalism that we saw above.

Since a priori physicalists hold that PTI → N is a priori, they are committed to denying P1) of the conceivability argument. The a priori physicalist, then, must argue that PTI and not Q, on ideal rational reflection, is incoherent or contradictory.[43]

A posteriori physicalists, on the other hand, generally accept P1) but deny P2)--the move from "conceivability to metaphysical possibility". Some a posteriori physicalists think that unlike the possession of most, if not all other empirical concepts, the possession of consciousness has the special property that the presence of PTI and the absence of consciousness will be conceivable—even though, according to them, it is knowable a posteriori that PTI and not Q is not metaphysically possible. These a posteriori physicalists endorse some version of what Daniel Stoljar (2005) has called "the phenomenal concept strategy".[44] Roughly speaking, the phenomenal concept strategy is a label for those a posteriori physicalists who attempt to show that it is only the concept of consciousness—not the property—that is in some way "special" or sui generis.[45] Other a posteriori physicalists[46] eschew the phenomenal concept strategy, and argue that even ordinary macroscopic truths such as "water covers 60% of the earth's surface" are not knowable a priori from PTI and a non-deferential grasp of the concepts "water" and "earth" et cetera. If this is correct, then we should (arguably) conclude that conceivability does not entail metaphysical possibility, and P2) of the conceivability argument against physicalism is false.[47]

Other views

Strawsonian physicalism

Galen Strawson's realistic physicalism (or "realistic monism") entails panpsychism – or at least micropsychism.[48][49][50] Strawson argues that "many—perhaps most—of those who call themselves physicalists or materialists [are mistakenly] committed to the thesis that physical stuff is, in itself, in its fundamental nature, something wholly and utterly non-experiential... even when they are prepared to admit with Eddington that physical stuff has, in itself, 'a nature capable of manifesting itself as mental activity', i.e. as experience or consciousness".[48] Because experiential phenomena allegedly cannot be emergent from wholly non-experiential phenomena, philosophers are driven to substance dualism, property dualism, eliminative materialism and "all other crazy attempts at wholesale mental-to-non-mental reduction".[48]

Real physicalists must accept that at least some ultimates are intrinsically experience-involving. They must at least embrace micropsychism. Given that everything concrete is physical, and that everything physical is constituted out of physical ultimates, and that experience is part of concrete reality, it seems the only reasonable position, more than just an 'inference to the best explanation'... Micropsychism is not yet panpsychism, for as things stand realistic physicalists can conjecture that only some types of ultimates are intrinsically experiential. But they must allow that panpsychism may be true, and the big step has already been taken with micropsychism, the admission that at least some ultimates must be experiential. 'And were the inmost essence of things laid open to us' I think that the idea that some but not all physical ultimates are experiential would look like the idea that some but not all physical ultimates are spatio-temporal (on the assumption that spacetime is indeed a fundamental feature of reality). I would bet a lot against there being such radical heterogeneity at the very bottom of things. In fact (to disagree with my earlier self) it is hard to see why this view would not count as a form of dualism... So now I can say that physicalism, i.e. real physicalism, entails panexperientialism or panpsychism. All physical stuff is energy, in one form or another, and all energy, I trow, is an experience-involving phenomenon. This sounded crazy to me for a long time, but I am quite used to it, now that I know that there is no alternative short of 'substance dualism'... Real physicalism, realistic physicalism, entails panpsychism, and whatever problems are raised by this fact are problems a real physicalist must face.[48]

— Galen Strawson, Consciousness and Its Place in Nature: Does Physicalism Entail Panpsychism?

See also


  1. ^ See Smart, 1959
  2. ^ a b c d e f g h Stoljar, Daniel (2009). Edward N. Zalta (ed.) (ed.). "Physicalism". The Stanford Encyclopedia of Philosophy (Fall 2009 Edition). Retrieved 2014-08-07.CS1 maint: Extra text: editors list (link)
  3. ^ Chalmers, D. (1996): The Conscious Mind, Oxford University Press, New York.
  4. ^ Zuboff, Arnold (1990). "One self: The logic of experience". Inquiry. 33 (1): 39–68. doi:10.1080/00201749008602210. ISSN 0020-174X.
  5. ^ Physicalism (Stanford Encyclopedia of Philosophy)
  6. ^ Karl Raimund Popper (2002). The Logic of Scientific Discovery. Psychology Press. ISBN 978-0-415-27844-7.
  7. ^ See Bennett and McLaughlin, 2011
  8. ^ See Putnam, 1967
  9. ^ See e.g., Smart, 1978; Lewis, 1994.
  10. ^ See e.g., Poland, 1994; Chalmers, 1996; Wilson, 2006.
  11. ^ Andrew Melnyk should apparently be credited with having introduced this name for Hempel's argument. See Melnyk, 1997, p.624
  12. ^ see Vincente, 2011
  13. ^ See Hempel, 1969, pp.180-183; Hempel, 1980, pp.194-195.
  14. ^ For a recent defence of the first horn see Melnyk, 1997. For a defence of the second, see Wilson, 2006.
  15. ^ See Jackson, 1998, p.7; Lycan, 2003.
  16. ^ See Papineau, 2002
  17. ^ See Montero, 1999
  18. ^ See Papineau and Montero, 2005
  19. ^ See e.g., Judisch, 2008
  20. ^ a b c d See Jackson, 1998
  21. ^ Lewis, David (1983). "New work for a theory of universals". Australasian Journal of Philosophy. 61 (4): 343–377. doi:10.1080/00048408312341131. ISSN 0004-8402.
  22. ^ Horgan, Terence (1982). "Supervenience and Microphysics". Pacific Philosophical Quarterly. 63 (January): 29–43.
  23. ^ Jackson, 1998
  24. ^ Chalmers, 1996
  25. ^ Where "metaphysical necessitation" here simply means that if "B" metaphysically necessitates "A" then any world in which B is instantiated is a world in which A is instantiated--a consequence of the metaphysical supervenience of A upon B. See Kripke, 1972.
  26. ^ See e.g., Stoljar, 2009, section 4.3.
  27. ^ See Hawthorne, 2002.
  28. ^ Chalmers, 1996, p.40.
  29. ^ Chalmers, 1996; Stoljar, 2009, section 4.3.
  30. ^ see Hawthorne, 2002, p.107
  31. ^ See Stoljar, 2010, p.138
  32. ^ a b Jaegwon Kim (26 November 1993). Supervenience and Mind: Selected Philosophical Essays. Cambridge University Press. ISBN 978-0-521-43996-1.
  33. ^ Melnyk, Andrew (1997). "How to Keep the 'Physical' in Physicalism". The Journal of Philosophy. 94 (12): 622. doi:10.2307/2564597. ISSN 0022-362X.
  34. ^ Smart, J. J. C. (1959). "Sensations and Brain Processes". The Philosophical Review. 68 (2): 141. doi:10.2307/2182164. ISSN 0031-8108.
  35. ^ Ernest Nagel (1961). The structure of science: problems in the logic of scientific explanation. Harcourt, Brace & World.
  36. ^ a b Fodor, J. A. (1974). "Special sciences (or: The disunity of science as a working hypothesis)". Synthese. 28 (2): 97–115. doi:10.1007/BF00485230. ISSN 0039-7857.
  37. ^ Bickle, J. (2006). Multiple realizability. In Stanford encyclopedia of philosophy. Available at Last revised in 2006, and last checked on May 27, 2009.
  38. ^ Byrne, A (1993). The Emergent Mind (Ph.D.). Princeton University.
  39. ^ a b See Chalmers and Jackson, 2001
  40. ^ See Chalmers, 2009.
  41. ^ See Nagel, 1974
  42. ^ See Chalmers, 2009
  43. ^ For a survey of the different arguments for this conclusion (as well as responses to each), see Chalmers, 2009.
  44. ^ See Stoljar, 2005
  45. ^ cf. Stoljar, 2005
  46. ^ e.g., Tye, 2009
  47. ^ For critical discussion, see Chalmers, 2009.
  48. ^ a b c d Strawson, Galen (2006). Consciousness and Its Place in Nature: Does Physicalism Entail Panpsychism?. Imprint Academic. pp. 4, 7. ISBN 978-1845400590. Archived from the original on 2012-01-11. I don't define the physical as concrete reality, as concrete-reality-whatever-it-is; obviously I can't rule out the possibility that there could be other non-physical (and indeed non-spatiotemporal) forms of concrete reality. I simply fix the reference of the term 'physical' by pointing at certain items and invoking the notion of a general kind of stuff. It is true that there is a sense in which this makes my use of the term vacuous, for, relative to our universe, 'physical stuff' is now equivalent to 'real and concrete stuff', and cannot be anything to do with the term 'physical' that is used to mark out a position in what is usually taken to be a substantive debate about the ultimate nature of concrete reality (physicalism vs immaterialism vs dualism vs pluralism vs…). But that is fine by me. If it's back to Carnap, so be it.
  49. ^ Lockwood, Michael (1991). Mind, Brain and the Quantum: The Compound 'I'. Blackwell Pub. pp. 4, 7. ISBN 978-0631180319. Archived from the original on 2016-03-04.
  50. ^ Skrbina, D. (2009). Mind That Abides: Panpsychism in the New Millennium. Advances in Consciousness Research. John Benjamins Publishing Company. p. 322. ISBN 9789027290038. LCCN 2008042603.


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External links

Causal closure

Physical causal closure is a metaphysical theory about the nature of causation in the physical realm with significant ramifications in the study of metaphysics and the mind. In a strongly stated version, physical causal closure says that "all physical states have pure physical causes" — Jaegwon Kim, or that "physical effects have only physical causes" — Agustin Vincente, p. 150.Those who accept the theory tend, in general although not exclusively, to the physicalist view that all entities that exist are physical entities. As Karl Popper says, "The physicalist principle of closedness of the physical ... is of decisive importance and I take it as the characteristic principle of physicalism or materialism."


In philosophy, emergentism is the belief in emergence, particularly as it involves consciousness and the philosophy of mind, and as it contrasts (or not) with reductionism. A property of a system is said to be emergent if it is a new outcome of some other properties of the system and their interaction, while it is itself different from them. Emergent properties are not identical with, reducible to, or deducible from the other properties. The different ways in which this independence requirement can be satisfied lead to variant types of emergence.

Exclusion principle (philosophy)

The exclusion principle is a philosophical principle that states:

If an event e causes event e*, then there is no event e# such that e# is non-supervenient on e and e# causes e*.

Functionalism (philosophy of mind)

Functionalism is a viewpoint of the theory of the mind (not to be confused with the psychological notion of one's Theory of Mind). It states that mental states (beliefs, desires, being in pain, etc.) are constituted solely by their functional role in, i.e. causal relations with, other mental states, sensory inputs and behavioral outputs. Functionalism developed largely as an alternative to the identity theory of mind and behaviorism.

Functionalism is a theoretical level between the physical implementation and behavioral output. Therefore, it is different from its predecessors of Cartesian dualism (advocating independent mental and physical substances) and Skinnerian behaviorism and physicalism (declaring only physical substances) because it is only concerned with the effective functions of the brain, through its organization or its "software programs".

Since mental states are identified by a functional role, they are said to be realized on multiple levels; in other words, they are able to be manifested in various systems, even perhaps computers, so long as the system performs the appropriate functions. While computers are physical devices with electronic substrate that perform computations on inputs to give outputs, so brains are physical devices with neural substrate that perform computations on inputs which produce behaviors.

Hempel's dilemma

Hempel's dilemma is a question first asked (at least on record) by the philosopher Carl Hempel. It has relevance to naturalism and physicalism in philosophy, and to philosophy of mind.

Index of philosophy of mind articles

This is a list of philosophy of mind articles.

Alan Turing

Alexius Meinong

Anomalous monism

Anthony Kenny

Arnold Geulincx

Association for the Scientific Study of Consciousness

Australian materialism

Baruch Spinoza

Biological naturalism

Brain in a vat

C. D. Broad

Chinese room



Consciousness Explained

Critical realism (philosophy of perception)

Daniel Dennett

David Hartley (philosopher)

David Kellogg Lewis

David Malet Armstrong

Direct realism

Direction of fit

Disquisitions relating to Matter and Spirit

Donald Davidson (philosopher)

Dream argument

Dualism (philosophy of mind)

Duration (Bergson)

Edmund Husserl

Eliminative materialism

Embodied philosophy

Emergent materialism

Evil demon

Exclusion principle (philosophy)

Frank Cameron Jackson

Fred Dretske

Functionalism (philosophy of mind)

G. E. M. Anscombe

Georg Henrik von Wright

George Edward Moore

Gilbert Harman

Gilbert Ryle

Gottfried Leibniz

Hard problem of consciousness

Henri Bergson

Hilary Putnam



Indefinite monism


Internalism and externalism

Intuition pump

J. J. C. Smart

Jaegwon Kim

Jerry Fodor

John Perry (philosopher)

John Searle

Karl Popper

Kendall Walton

Kenneth Allen Taylor

Ludwig Wittgenstein

Mad pain and Martian pain

Mental property

Methodological solipsism

Michael Tye (philosopher)


Mind-body dichotomy


Multiple Drafts Model

Multiple realizability

Naming and Necessity

Naïve realism


Neutral monism

Noam Chomsky

Parallelism (philosophy)

Personal identity


Philosophy of artificial intelligence

Philosophy of mind

Philosophy of perception


Pluralism (philosophy)

Privileged access

Problem of other minds

Property dualism

Psychological nominalism


Reflexive monism

René Descartes

Representational theory of mind

Richard Rorty

Ron McClamrock

Self (philosophy)

Society of Mind


Stephen Stich

Subjective idealism


Sydney Shoemaker

Tad Schmaltz

The Concept of Mind

The Meaning of Meaning

Thomas Nagel

Turing test

Type physicalism

Unconscious mind

Wilfrid Sellars

William Hirstein

William James

Jaegwon Kim

Jaegwon Kim (born September 12, 1934) is a Korean-American philosopher who is now an emeritus professor at Brown University, but who also taught at several other leading American universities. He is best known for his work on mental causation, the mind-body problem and the metaphysics of supervenience and events. Key themes in his work include: a rejection of Cartesian metaphysics, the limitations of strict psychophysical identity, supervenience, and the individuation of events. Kim's work on these and other contemporary metaphysical and epistemological issues is well represented by the papers collected in Supervenience and Mind: Selected Philosophical Essays (1993).

Knowledge argument

The knowledge argument (also known as Mary's room or Mary the super-scientist) is a philosophical thought experiment proposed by Frank Jackson in his article "Epiphenomenal Qualia" (1982) and extended in "What Mary Didn't Know" (1986). The experiment is intended to argue against physicalism—the view that the universe, including all that is mental, is entirely physical. The debate that emerged following its publication became the subject of an edited volume—There's Something About Mary (2004)—which includes replies from such philosophers as Daniel Dennett, David Lewis, and Paul Churchland.


Materialism is a form of philosophical monism which holds that matter is the fundamental substance in nature, and that all things, including mental aspects and consciousness, are results of material interactions.

In Idealism, mind and consciousness are first-order realities to which matter is subject and secondary. In philosophical materialism the converse is true. Here mind and consciousness are by-products or epiphenomena of material processes (the biochemistry of the human brain and nervous system, for example) without which they cannot exist. According to this doctrine the material creates and determines consciousness, not vice versa.

Materialist theories are mainly divided into three groups. Naive materialism identifies the material world with specific elements (e.g. the scheme of the four elements—fire, air, water and earth—devised by the pre-Socratic philosopher Empedocles). Metaphysical materialism examines separated parts of the world in a static, isolated environment. Dialectical materialism adapts the Hegelian dialectic for materialism, examining parts of the world in relation to each other within a dynamic environment.

Materialism is closely related to physicalism, the view that all that exists is ultimately physical. Philosophical physicalism has evolved from materialism with the theories of the physical sciences to incorporate more sophisticated notions of physicality than mere ordinary matter, such as: spacetime, physical energies and forces, dark matter, and so on. Thus the term "physicalism" is preferred over "materialism" by some, while others use the terms as if they are synonymous.

Philosophies contradictory to materialism or physicalism include idealism, pluralism, dualism, and other forms of monism.

Mental event

A mental event is anything which happens within the mind or mind substitute of a conscious individual. Examples include thoughts, feelings, decisions, dreams, and realizations.Some believe that mental events are not limited to human thought but can be associated with animals and artificial intelligence as well. Whether mental events are identical to complex physical events, or whether such an identity even makes sense, is central to the mind-body problem.

Mind–body dualism

Mind–body dualism, or mind–body duality, is a view in the philosophy of mind that mental phenomena are, in some respects, non-physical, or that the mind and body are distinct and separable. Thus, it encompasses a set of views about the relationship between mind and matter, and between subject and object, and is contrasted with other positions, such as physicalism and enactivism, in the mind–body problem.Aristotle shared Plato's view of multiple souls and further elaborated a hierarchical arrangement, corresponding to the distinctive functions of plants, animals, and people: a nutritive soul of growth and metabolism that all three share; a perceptive soul of pain, pleasure, and desire that only people and other animals share; and the faculty of reason that is unique to people only. In this view, a soul is the hylomorphic form of a viable organism, wherein each level of the hierarchy formally supervenes upon the substance of the preceding level. Thus, for Aristotle, all three souls perish when the living organism dies. For Plato however, the soul was not dependent on the physical body; he believed in metempsychosis, the migration of the soul to a new physical body.Dualism is closely associated with the thought of René Descartes (1641), which holds that the mind is a nonphysical—and therefore, non-spatial—substance. Descartes clearly identified the mind with consciousness and self-awareness and distinguished this from the brain as the seat of intelligence. Hence, he was the first to formulate the mind–body problem in the form in which it exists today. Dualism is contrasted with various kinds of monism. Substance dualism is contrasted with all forms of materialism, but property dualism may be considered a form of emergent materialism or non-reductive physicalism in some sense.

Nancey Murphy

Nancey Murphy is an American philosopher and theologian who is Professor of Christian Philosophy at Fuller Theological Seminary, Pasadena, CA. She received the B.A. from Creighton University (philosophy and psychology) in 1973, the Ph.D. from University of California, Berkeley (philosophy of science) in 1980, and the Th.D. from the Graduate Theological Union (theology) in 1987.

Non-physical entity

In ontology and the philosophy of mind, a non-physical entity is a spirit or being that exists outside physical reality. Their existence divides the philosophical school of physicalism from the schools of idealism and dualism; with the latter schools holding that they can exist and the former holding that they cannot. If one posits that non-physical entities can exist, there exist further debates as to their inherent natures and their position relative to physical entities.

Philosophical zombie

The philosophical zombie or p-zombie argument is a thought experiment in philosophy of mind and philosophy of perception that imagines a being that, if it could conceivably exist, logically disproves the idea that physical stuff is all that is required to explain consciousness. Such a zombie would be indistinguishable from a normal human being but lack conscious experience, qualia, or sentience. For example, if a philosophical zombie were poked with a sharp object it would not inwardly feel any pain, yet it would outwardly behave exactly as if it did feel pain. The argument sometimes takes the form of hypothesizing a zombie world, indistinguishable from our world, but lacking first person experiences in any of the beings of that world.

Philosophical zombie arguments are used in support of mind-body dualism against forms of physicalism such as materialism, behaviorism and functionalism. It's an argument against the idea that the "hard problem of consciousness" (accounting for subjective, intrinsic, first person, what-it's-like-ness) could be answered by purely physical means. Proponents of the argument, such as Australian philosopher David Chalmers, argue that since a zombie is defined as physiologically indistinguishable from human beings, even its logical possibility would be a sound refutation of physicalism, because it would establish the existence of conscious experience as a further fact. However, physicalists like Daniel Dennett counter that philosophical zombies are logically incoherent and thus impossible.

Philosophy of mind

Philosophy of mind is a branch of philosophy that studies the ontology, nature, and relationship of the mind to the body. The mind–body problem is a paradigm issue in philosophy of mind, although other issues are addressed, such as the hard problem of consciousness, and the nature of particular mental states. Aspects of the mind that are studied include mental events, mental functions, mental properties, consciousness, the ontology of the mind, the nature of thought, and the relationship of the mind to the body.

Dualism and monism are the two central schools of thought on the mind–body problem, although nuanced views have arisen that do not fit one or the other category neatly. Dualism finds its entry into Western philosophy thanks to René Descartes in the 17th century. Substance dualists like Descartes argue that the mind is an independently existing substance, whereas property dualists maintain that the mind is a group of independent properties that emerge from and cannot be reduced to the brain, but that it is not a distinct substance.Monism is the position that mind and body are not ontologically distinct entities (independent substances). This view was first advocated in Western philosophy by Parmenides in the 5th century BCE and was later espoused by the 17th-century rationalist Baruch Spinoza. Physicalists argue that only entities postulated by physical theory exist, and that mental processes will eventually be explained in terms of these entities as physical theory continues to evolve. Physicalists maintain various positions on the prospects of reducing mental properties to physical properties (many of whom adopt compatible forms of property dualism), and the ontological status of such mental properties remains unclear. Idealists maintain that the mind is all that exists and that the external world is either mental itself, or an illusion created by the mind. Neutral monists such as Ernst Mach and William James argue that events in the world can be thought of as either mental (psychological) or physical depending on the network of relationships into which they enter, and dual-aspect monists such as Spinoza adhere to the position that there is some other, neutral substance, and that both matter and mind are properties of this unknown substance. The most common monisms in the 20th and 21st centuries have all been variations of physicalism; these positions include behaviorism, the type identity theory, anomalous monism and functionalism.Most modern philosophers of mind adopt either a reductive physicalist or non-reductive physicalist position, maintaining in their different ways that the mind is not something separate from the body. These approaches have been particularly influential in the sciences, especially in the fields of sociobiology, computer science (specifically, artificial intelligence), evolutionary psychology and the various neurosciences. Reductive physicalists assert that all mental states and properties will eventually be explained by scientific accounts of physiological processes and states. Non-reductive physicalists argue that although the mind is not a separate substance, mental properties supervene on physical properties, or that the predicates and vocabulary used in mental descriptions and explanations are indispensable, and cannot be reduced to the language and lower-level explanations of physical science. Continued neuroscientific progress has helped to clarify some of these issues; however, they are far from being resolved. Modern philosophers of mind continue to ask how the subjective qualities and the intentionality of mental states and properties can be explained in naturalistic terms.

Property (philosophy)

In mathematics, logic, and philosophy, a property is a characteristic of an object; a red object is said to have the property of redness. The property may be considered a form of object in its own right, able to possess other properties. A property, however, differs from individual objects in that it may be instantiated, and often in more than one thing. It differs from the logical/mathematical concept of class by not having any concept of extensionality, and from the philosophical concept of class in that a property is considered to be distinct from the objects which possess it. Understanding how different individual entities (or particulars) can in some sense have some of the same properties is the basis of the problem of universals. The terms attribute and quality have similar meanings.

Property dualism

Property dualism describes a category of positions in the philosophy of mind which hold that, although the world is composed of just one kind of substance—the physical kind—there exist two distinct kinds of properties: physical properties and mental properties. In other words, it is the view that non-physical, mental properties (such as beliefs, desires and emotions) inhere in or supervene upon certain physical substances (namely brains). As a doctrine, 'property dualism' is epistemic, as distinct from ontic.

Substance dualism, on the other hand, is the view that there exist in the universe two fundamentally different kinds of substance: physical (matter) and non-physical (mind or consciousness), and subsequently also two kinds of properties which adhere in those respective substances. Substance dualism is thus more susceptible to the mind-body problem. Both substance and property dualism are opposed to reductive physicalism. As a doctrine, 'substance dualism' is ontic, as distinct from epistemic.


In philosophy, supervenience refers to a relation between sets of properties or sets of facts. X is said to supervene on Y if and only if some difference in Y is necessary for any difference in X to be possible. Equivalently, X is said to supervene on Y if and only if X cannot vary unless Y varies. Here are some examples.

Whether there is a table in the living room supervenes on the positions of molecules in the living room.

The truth value of (A) supervenes on the truth value of (¬A).

Molecular properties supervene on atomic properties.

The quality of Nixon’s moral character supervenes on how he is disposed to act.These are examples of supervenience because in each case the truth values of some propositions cannot vary unless the truth values of some other propositions vary.

Supervenience is of interest to philosophers because it differs from other nearby relations, for example entailment. Some philosophers believe it possible for some A to supervene on some B without being entailed by B. In such cases it may seem puzzling why A should supervene on B and equivalently why changes in A should require changes in B. Two important applications of supervenience involve cases like this. One of these is the supervenience of mental properties (like the sensation of pain) on physical properties (like the firing of ‘pain neurons’). A second is the supervenience of normative facts (facts about how things ought to be) on natural facts (facts about how things are).

These applications are elaborated below. But an illustrative note bears adding here. It is sometimes claimed (and has been claimed in earlier versions of this entry) that what is at issue in these problems is the supervenience claim itself. For example, it has been claimed that what is at issue with respect to the mind-body problem is whether mental phenomena do in fact supervene on physical phenomena. This is incorrect. It is by and large agreed that some form of supervenience holds in these cases: Pain happens when the appropriate neurons fire. The disagreement is over why this is so. Materialists claim that we observe supervenience because the neural phenomena entail the mental phenomena, while dualists deny this. The dualist’s challenge is to explain supervenience without entailment.

The problem is similar with respect to the supervenience of normative facts on natural facts. It is agreed that facts about how persons ought to act are not entailed by natural facts but cannot vary unless natural facts vary, and this rigid binding without entailment might seem puzzling.

The possibility of "supervenience without entailment" or "supervenience without reduction" is contested territory among philosophers.

Type physicalism

Type physicalism (also known as reductive materialism, type identity theory, mind–brain identity theory and identity theory of mind) is a physicalist theory, in the philosophy of mind. It asserts that mental events can be grouped into types, and can then be correlated with types of physical events in the brain. For example, one type of mental event, such as "mental pains" will, presumably, turn out to be describing one type of physical event (like C-fiber firings).

Type physicalism is contrasted by token identity physicalism, which argues that mental events are unlikely to have "steady" or categorical biological correlates. These positions make use of the philosophical type–token distinction (e.g., Two persons having the same "type" of car need not mean that they share a "token", a single vehicle). Type physicalism can now be understood to argue that there is identicalness between types, whereas token identity physicalism says one can only describe a particular, unique, brain event.

There are other ways a physicalist might criticize type physicalism; eliminative materialism and revisionary materialism question whether science is currently using the best categorisations. In the same way talk of demonic possession was questioned with scientific advance, categorisations like "pain" may need to be revised.

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