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Physicalism is the metaphysical position (associated particularly with Quine) that everything is physical; that is, that there are no kinds of things other than physical things. Likewise, physicalism about the mental is a position in philosophy of mind which holds that the mind is a physical thing in some sense. This position is also called "materialism", but the term "physicalism" is preferable because it does not have any misleading ethical connotations, and because it carries an emphasis on the physical, meaning whatever is described ultimately by physics -- not just matter but energy and whatever else physical theories might talk about. Some proposed examples might be space, time, physical forces, structure, physical processes,information, state, et al.

The term physicalism was coined by Otto Neurath, in a series of early 20th century essays on the subject, in which he wrote

According to physicalism, the language of physics is the universal language of science and, consequently, any knowledge can be brought back to the statements on the physical objects.

Because it claims that only physical things exist, physicalism is a form of monism. The opposite of physicalism is subjective idealism, as exemplified by the metaphysics proposed by George Berkeley, which holds that there is no physical reality at all. In this view, all that exists is mental or spiritual: it is thus also monistic. It is also in opposition to neutral monism, a philosophy advocated by Baruch Spinoza that states that only one substance exists, but that this substance is neither physical or mental.

The rest of this article discusses physicalism about the mental: this is merely a specific application of physicalism as described above. Physicalism about the mental contrasts with mind-body dualism, which claims that the physical and the mental are two different sorts of things and thus that the mind is non-physical, and exists in a different metaphysical category and realm.



Chart demonstrating how one set (A) supervenes on another set (B).


Donald Davidson formalised the idea of supervenience.

Supervenience is the relationship between a higher level and lower level where the higher level is dependent on the lower level. This means that one level supervenes on another if and only if a change in the lower level causes a change in the higher level (e.g. a set of properties A supervenes upon a set of properties B when there cannot be an A difference without a B difference). In physicalism, superveniences establishes a relationship between the mental and the physical, so that any change in the mental is caused by a change in the physical. Just as a shadow is dependent upon the position of the object causing it, so is the mental dependent upon the physical. Physicalism thusly implies (through modal realism) that:

No two worlds could be identical in every physical respect yet differ in some other respect.

The corresponding conclusion about the mental would be as follows:

No two beings, or things could be identical in every physical respect yet differ in some mental respect.

However, supervenience physicalism alone does not establish minimal physicalism. It is possible that mental or other non-physical states supervene upon the physical. As this allows for the possibility that the mind is causally inefficacious and only contingently related to the physical, supervenience physicalism is compatible with epiphenomenalism. However, when supervenience physicalism and token physicalism are combined, minimal physicalism is met, as will be detailed in the following sections.

Arguments against supervenience

Although supervenience seems to be perfectly suited to explain the predictions of physicalism (i.e. the mental is dependent on the physical), there are four main problems with it. They are Ephiphenomenal ectoplasm, the lone ammonium molecule problem, modal status problem and the problem of necessary beings.

Epiphenomenal ectoplasm

Epiphenomenal ectoplasm was proposed by Horgan and Lewis in 1983, in which they stated, a possible world (a world that could possibly exist) W is identical to our world in the distribution of all mental and physical characteristics (i.e. they are identical), except world W contains an experience called epiphenomenal ectoplasm that does not causally interact with that world. If supervenience physicalism is true, then such a world could not exist because a physical duplicate of the actual world (the world that is known to exist) could not possess an epiphenomenal ectoplasm. This was rectified by Frank Jackson, by adjusting the application of supervenience within physicalism to state "Physicalism is true at a possible world W if and only if any world which is a minimal physical duplicate (i.e. identical) of W is a duplicate of W simpliciter."

The lone ammonium molecule problem

The lone ammonium molecule problem provides a problem for Jackson's solution to epiphenomenal ectoplasm. It was proposed by Jaegwon Kim in 1993 when he stated that according to Jackson's idea of supervenience, a possible world W was identical to the actual world, except it possessed an extra ammonium molecule on one of Saturn’s rings. This may not seem to provide much of a problem, but because Jackson's solution refers only to minimal physical duplicates, this allows for the mental properties of W to be vastly different than in the actual world. If such a difference would cause mental differences on Earth, it would not prove our misunderstanding of physicalism.

Modal status problem

The modal status problem is only problematic if one thinks of physicalism as a contingent truth (i.e. not necessary), because it is described in terms of modal notions (i.e. through modal realism). The problem is presented when one takes the statement "Minimal physical truths entail all truths", from this one takes the statement "S (a statement that describes all minimal physical truths) entails S* (a statement that describes the world)". This statement is a necessary truth, and therefore supervenience physicalism could not be contingent. The solution to this is to accept the above statement not as the equivalent of physicalism, but as an entailment of it.

Problem of necessary beings

The problem of necessary beings was proposed by Jackson in 1998, in which he stated that a necessary being exists in all possible worlds as a non-physical entity, and therefore proves physicalism false. However, physicalism allows for the existence of necessary beings, because any minimal physical duplicate would have the same mental properties as the actual world. This however is paradoxical, based on the fact that physicalism both permits and prevents the existence of such beings. However, the existence of necessary beings is paradoxical in itself. They are both distinct from the physical world and dependent upon it. This violates Hume's fork which states, "there are no necessary connections between distinct existences".

Token and Type

Physicalism is divided into two branches, depending upon its support of supervenience: Token and Type. Both are ontologically reductionist, as they reduce mental states and processes into physical states and processes. This should not be misinterpreted as meaning that mental events are reduced into neurological states and process, as this is true only of type physicalism. (See Reductive physicalism).

Token physicalism

Token physicalism states "for every actual particular (i.e. object, event or process) x, there is some physical particular y such that x=y". This does not entail nor is entailed by supervenience, although if supervenience is true, it does not necessarily rule out token physicalism. The difference between supervenience and token physicalism is simple; token physicalism states that for every mental particular there is a physical particular to which it is identical, while supervenience physicalism states that set A (e.g. mental properties) cannot change unless set B (e.g. physical properties) changes as well. (i.e. A supervenes on B).

Still, token physicalism presents at least two problems. It requires that for social, moral, and psychological particulars there must be a physical particular identical with them. Consider the Supreme Court of the United States. The Supreme Court exists, but according to token physicalism, there is a physical object that is identical to the Supreme Court. However, this physical particular does not necessarily exist in any conventional use of the word 'physical'. Supervenience escapes this problem as the social, moral, and psychological particulars are said to supervene on the physical particulars that compose them. Another problem is that token physicalism does not capture minimal physicalism, meaning that it does not capture the core commitment of physicalism, i.e. that everything is physical. Simply because every particular has a physical property does not rule out the possibility that some particulars have non-supervenient mental properties. This shows that token physicalism supports property dualism and therefore does not entail minimal physicalism. However, if one accepts both supervenience physicalism and token physicalism, then minimal physicalism is met as supervenience physicalism is not compatible with property dualism. [1]

Type physicalism

Main article: Type physicalism

Type physicalism (also known as Type Identity Theory, Type-Type theory or just Identity Theory) is the theory, in the philosophy of mind, which asserts that mental events are type-identical to the physical events in the brain with which they are correlated. It is called type identity in order to distinguish it from a similar but distinct theory called the token identity theory.

The type/token distinction is easily illustrated by way of example. In the phrase "yellow is yellow is yellow is yellow", there are only two types of words ("yellow" and "is") but there are seven tokens (four of one and three of the other). The thesis of type physicalism consists in the idea that mental event types (e.g. pain in all individual organisms of all species at all times) are, at least contingently, identical with specific event types in the brain (e.g. C-fibre firings in all individual organisms of all species and at all times).

If type physicalism is true then mental state M1 would be identical to brain state B1. This seems quite unlikely, as it would imply that the mental state of pain, for example, would perfectly correlate to a specific brain state in all organisms at all times. Many avoid this problem by saying that mental states can not be reduced to a specific brain state as they are multiply realizable. That is, the same mental state can be produced from many different physical states. Token physicalism states that for every particular or occurrence, there is a physical particular with which it is identical. Therefore, while the mental state of pain or happiness is not type-identical to any specific brain state, it is still physical.


According to Ullin Place, one of the popularizers of the idea of type-identity in the 1950s and '60s, the idea of type-identical mind/body physicalism originated in the 1930s with the psychologist E. G. Boring and took nearly a quarter of a century to finally catch on and become accepted by the philosophical community. Boring, in a book entitled The Physical Dimensions of Consciousness (1933) wrote that:

To the author a perfect correlation is identity. Two events that always occur together at the same time in the same place, without any temporal or spatial differentiation at all are not two events but the same event. The mind-body correlations as formulated at present, do not admit of spatial correlation, so they reduce to matters of simple correlation in time. The need for identification is no less urgent in this case.

The barrier to the acceptance of any such vision of the mind, according to Place, was that philosophers and logicians had not yet taken a substantial interest in questions of identity and referential identification in general. The dominant epistemology of the logical positivists at that time was phenomenalism, in the guise of the theory of sense-data. Indeed Boring himself subscribed to the phenomenalist creed, attempting to reconcile it with an identity theory and this resulted in a reductio ad absurdum of the identity theory, since brain states would have turned out, on this analysis, to be identical to colors, shapes, tones and other sensory experiences.

The revival of interest in the work of Gottlob Frege and his ideas of sense and reference on the part of Herbert Feigl and J.J.C. Smart, along with the discrediting of phenomenalism through the influence of the later Wittgenstein and J.L. Austin, led to a more tolerant climate toward physicalistic and realist ideas. Logical behaviorism emerged as a serious contender to take the place of the Cartesian "ghost in the machine" and, although not lasting very long as a dominant position on the mind/body problem, its elimination of the whole realm of internal mental events was strongly influential in the formation and acceptance of the thesis of type identity.

A priori and A posteriori

Physicalism is then further divided depending on whether it can be known a priori or a posteriori: If physicalism is true, S is the statement that describes the entire physical nature of the world collectively, and S* is the statement that describes the entire nature of the world. S entails S*.

A priori physicalism is that, which assumes that the above can be known without observation (i.e. independently from experience). Originally it was assumed that physicalism was a priori, until Kripke published Naming and Necessity in 1980, which proposed the idea that there are truths that are both necessary and a posteriori.

A posteriori physicalism is that, which holds physicalism as a necessary truth that is known a posteriori (i.e. known through empirical observation). There are two main interpretations of a posteriori physicalism which exist today. One is that, a posteriori truth can be reached a priori by contingent a posteriori truths. The other holds that there are a posteriori truths that are taken from non-contingent (i.e. necessary) truths. A problem arises when the former is combined with the above statement (S entails S*). This problem is that according to the former there is a contingent truth that entails the above statement S#, so that S and S# then S*[2]. However, if S describes the nature of the physical word collectively, it seems that S# is already included in S. Therefore, the truth is not a posteriori after all, but merely the same statement knowable a priori. The a posteriori physicalist must then turn to the alternative interpretation that there are non-contingent a posteriori truths. However, this view remains very controversial within analytic philosophy and it remains an unsettled question.

Reductive physicalism

A doctrine stating that everything in the world can be reduced down to its fundamental physical, or material, basis. For this reason, the word "physicalism" is often used interchangeably with the word "materialism." Both terms hold that the real world consists only of matter and energy, and that all organic and inorganic processes can be explained by reference to the laws of nature. Physics, the main branch of science generally supporting this view, has been able to explain a large range of phenomena in terms of a few of these basic natural laws; such as gravity, electricity, composition of mass, etc. [3]

Before Donald Davidson introduced the concept of supervenience to physicalism, reductionism was widely held by many physicalists. However, it is now questioned whether non-reductive physicalism is coherent or if physicalism entails reductionism. One proposed solution to this is to analyze in other terms. One states “Reductionism is true if and only if for every mental predicate F, there is a physical predicate G so that ‘x is F if and only if x is G’. The problem with this is that it has remained unsupported by physicalist since before 1959, when J.J.C. Smart proposed a topic neutral {i.e. it describes terms of neither the physical nor mental); this means that the above statement can be rejected, being considered one of the greatest innovations in philosophy of mind.

However, as this was applied to philosophy of science by Ernest Nagel, as a bridge law, it provided a problem. He concluded “Reductionism is true if and only if for each mental predicate F there is a neurological predicate G such that a sentence of the form ‘x is F if and only if x is G’”. The problem is that one psychological process may be caused by many neurological processes, and possible non-neurological processes causing it to be false.

A third idea is present; it states “Reductionism is true if and only if for each mental predicate F there is non-mental predicate G such that a sentence of the form 'if x is F then x is G' is a priori”. This kind follows the identity theory, and therefore is tied to supervenience, and is reliant on a priori truth.

Non-reductive physicalism

Non-reductive physicalism is the idea that while mental states are physical they are not reducible to physical properties. Donald Davidson proposed anomalous monism as a non-reductive physicalism. Supervenience physicalism (also proposed by Donald Davidson) is a non-reductive physicalism, as mental events supervene (i.e. physical properties are identical to mental properties) on physical events rather than mental events reducing to physical events. For example if we accept supervenience physicalism, if you were to be electrocuted, the pain you would feel would supervene on the firing of your c-fibres. If we accept, reductive physicalism, the pain would be those c-fibres firing.

Jaegwon Kim

Figure demonstration how M1 and M2 are not reduced to P1 and P2.

In response to Davidson's anomalous monism, Kim proposed that one cannot be a physicalist and a non-reductivist. He proposes (using the chart on the right) that M1 causes M2 (these are mental events) and P1 causes P2 (these are physical events). P1 realises M1 and P2 realises M2. However M1 does not causally effect P1 (i.e. M1 is a consequent event of P1). If P1 causes P2, and M1 is a result of P1, then M2 is a result of P2. He says that the only alternatives this problem is to accept dualism (where the mental events are independent of the physical events) or eliminativism (where the mental events do not exist).


Main article: Materialism

In philosophy, materialism is that form of physicalism which holds that the only thing that can truly be said to exist is matter; that fundamentally, all things are composed of material and all phenomena are the result of material interactions. Science uses a working assumption, sometimes known as methodological naturalism, that observable events in nature are explained only by natural causes without assuming the existence or non-existence of the supernatural. As a theory, materialism belongs to the class of monist ontology. As such, it is different from ontological theories based on dualism or pluralism. In terms of singular explanations of the phenomenal reality, materialism stands in sharp contrast to idealism. Alternate definition: materialism postulates that matter is ontologically primary to existence of the idealistic phenomena, and that the latter cannot exist separately from the former. This definition does not deny existence of such idealistic (i.e., non-material) phenomena as space, time, mind, or even information outside of human consciousness. Thus, it is not nominalistic or strictly monistic, but it does say that these phenomena cannot exist separately from the matter that "creates" them. Materialistic brain leads to the existence of idealistic mind, which disappears with destruction of the brain; materialistic doughnut leads to the existence of idealistic doughnut hole, and the latter exists independently of the human mind. The ideal phenomena mentioned refer to the "phenomena [that] are result of material interactions" and the "material interactions" and relationships themselves, mentioned but not defined in the first definition. They do not refer to the supernatural phenomena.

Arguments for physicalism

Exclusion principle

One argument is the exclusion principle, which states that 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*. This comes when one poses this scenario; One usually considers that the desire to lift one’s arm as a mental event, and the lifting on one's arm, a physical event. According to the exclusion principle, there must be an event an event that does not supervene on e while causing e*. This is interpreted as meaning, mental events supervene upon the physical. However, some philosophers accept epiphenomenalism, which states mental events are caused by physical events, but physical events are not caused by mental events. However, If e# does not cause e, then there is no way to verify that e* exists. Yet, this debate has not been settled in the philosophical community.[4].

Argument from methodological naturalism

The argument from methodological naturalism has two premises. First, it is rational to form one's metaphysical beliefs based on the methods of natural science. Secondly, the metaphysical worldview which one is led to by the methods of natural science is physicalism. Thus, it is most likely that physicalism is true. One reply to this argument is to reject the second premise and state that one is not led to physicalism by the natural sciences. However, this does not seem to have much support. While there are other options when considering the nature of the world, panpsychism in cognitive science, or vitalism in biology, this is irrelevant. The argument merely states that physicalism is the most likely, not that other views are impossible.

Arguments against physicalism

Knowledge argument

Though there have been many objections to physicalism throughout its history, many of these arguments concern themselves with the apparent contradiction of the existence of qualia in an entirely physical world. The most popular argument of this kind is the so-called knowledge argument as formulated by Frank Jackson. The argument asks us to consider Mary, a young girl who has been covered in black and white paint, along with the room in which she lives for her entire life. However, she is allowed access to a large amount of books, containing all physical knowledge within them. During her time in the room, she eventually comes to know all of the physical facts about the world, including all of the physical facts about color. Now, to the physicalist, it would seem that this would entail Mary knowing everything about the world. However, once she is let out of her room and into the world, it becomes apparent that Mary does not know everything about the world, such as the feeling or experience of seeing color. If Mary did not have such knowledge, how can it be said that everything supervenes upon the physical?

One way the physicalist may respond to this argument is through the ability hypothesis, developed by Lawrence Nemerow and David Lewis. The ability hypothesis draws a distinction between propositional knowledge, such as 'Mary knows that the sky is typically blue during the day', and knowledge-how, such as 'Mary knows how to climb a mountain'. It then states that all that Mary gains from her experience is knowledge-how. This argument shows that while Mary does gain knowledge from her experience, it is not the propositional knowledge which would need to be obtained if the knowledge argument were to be logically sound [5]. (See also: Mary's room.)

Argument from philosophical zombies

The zombie argument is a thought experiment that attempts to show that it is conceivable, and therefore possible, that an organism that is physically identical to a conscious being may itself, lack consciousness or qualia. Though few think zombies are nomologically possible, that is, possible in our world, some philosophers do argue that they are metaphysically possible. This poses a problem for the physicalist as the metaphysical possibility of zombies would entail that mental states do not supervene upon physical states, a claim that the physicalist is committed to. It is then the burden of the physicalist to show that zombies are not conceivable, or if they are conceivable, that they are not metaphysically possible.

One argument against the conceivablility of zombies comes from Daniel Dennett who argues that, "when philosophers claim that zombies are conceivable, they invariably underestimate the task of conception (or imagination), and end up imagining something that violates their own definition". Dennett, in The Unimagined Preposterousness of Zombies (1995) compares consciousness to health.

Supposing that by an act of stipulative imagination you can remove consciousness while leaving all cognitive systems intact — a quite standard but entirely bogus feat of imagination — is like supposing that by an act of stipulative imagination, you can remove health while leaving all bodily functions and powers intact. … Health isn't that sort of thing, and neither is consciousness.

However, the previous argument notwithstanding, does the conceivability of zombies entail their possibility? One response rests on the concept of the nature of qualia. If certain non-physical properties exist which match our conception of qualia, then such non-physical properties would be qualia, and zombies would be conceivable and possible. However, if there are no non-physical properties, then what we think of as qualia, are the physical properties which perform the functional tasks of what we conceive of as qualia. In this scenario, zombies would not be conceivable. Through this approach to the problem, physicalists can accept that the possibility of zombies is conceivable, while simultaneously denying that zombies are possible. [6]


Jack Angstreich Screaming At Brenda During Physicalism Debate-3

See also



External links

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