The term dualism has a number of uses in philosophy, but perhaps the most common is to describe positions on the mind-body problem that hold that the mind cannot be identified with the body or part of the body, or that mental properties are not physical properties.

The form of dualism Descartes advocated is called Cartesian dualism or interactive dualism. The mind is that which is responsible for mental states of all kinds, including sensation, perception, thought, emotion, deliberation, decision, and intentional action. Some philosophers maintain

that this role is played by the brain, but Descartes argued that this could not be so. His view was that the mind was a separate thing, or substance, that causally interacted with the brain, and through it with the rest of the body and the

rest of the world. Sensation and perception involve states of the world affecting states of sense organs, which in turn affect the brain, which causes the mind to be in certain states. Action involves states of mind affecting the brain, which in turn affects the body, which may interact with other things in the world.

Other forms of dualism include epiphenomenalism,

parallelism, and property dualism. The epiphenomenalist holds that the body affects the mind, but not vice versa. The mind only appears to affect the body, because the apparent mental causes of bodily changes (like the decision to lift my arm) coincide with the true bodily causes (some change in my brain). Parallelists hold that mind and body are two substances that do not interact at all. Property dualism maintains that the mind can be identified with the brain (or with the body as a whole), but mental properties cannot be reduced to physical ones. On this view, it is my

brain that is responsible for sensation, perception,and other mental phenomena. But the fact that my brain is thinking a certain thought, for example, is an additional fact about it, one that cannot be reduced to any of its physical properties.