Physicalism

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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 our best physical theories might talk about. Because it claims that only physical things exist, physicalism is a form of monism.

The opposite of physicalism is subjective idealism, such as 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.

The rest of this article discusses physicalism about the mental, although it should be noted that 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.

Type and token physicalism
The form of physicalism about the mental known as identity materialism identifies the mental with the physical. In other words, it makes the claim that the mental is the physical. This identity often takes one of two different forms:


 * Token physicalism holds that for every mental particular there is a physical particular with which it is identical.
 * Type physicalism holds that every mental property is identical with a physical property.

Supervenience
The general physicalist claim described in the introduction to this article implies that everything there is supervenes on the physical. If the mind supervenes on the physical body, then any mental change must be the result of a physical change, just as a shadow can only change when the object which causes it (or the light illuminating that object) changes. Physicalism thus implies 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 people (or beings, or things) could be identical in every physical respect yet differ in some mental respect.

Note however that the claim that everything supervenes on the physical is not sufficient for physicalism since it is possible to hold that non-physical properties or substances supervene on the physical. See epiphenomenalism.

Reductive physicalism
One form of physicalism claims that the mental is reducible to the physical. To claim that one thing (X) is reducible to another (Y) is to hold that whenever one discusses X, one can be understood to be talking about Y instead. Thus, the claim of reductive physicalism is that when we talk about mental events, we can be understood to be talking about events that are made up entirely of matter and energy.

Sources and further reading

 * The Stanford Encyclopedia of Philosophy's entry on physicalism.

Physikalismus Physicalisme Fisicalismo Физикализм