Free will
Mind–body problem

The idea of free will is one aspect of the mind–body problem, that is, consideration of the relation between mind (for example, consciousness, memory, and judgment) and body (for example, the human brain and nervous system). Philosophical models of mind are divided into physical and non-physical expositions.

Cartesian dualism holds that the mind is a nonphysical substance, the seat of consciousness and intelligence, and is not identical with physical states of the brain or body. It is suggested that although the two worlds do interact, each retains some measure of autonomy. Under cartesian dualism external mind is responsible for bodily action, although unconscious brain activity is often caused by external events (for example, the instantaneous reaction to being burned). Cartesian dualism implies that the physical world is not deterministic – and in which external mind controls (at least some) physical events, providing an interpretation of incompatibilist free will. Stemming from Cartesian dualism, a formulation sometimes called interactionalist dualism suggests a two-way interaction, that some physical events cause some mental acts and some mental acts cause some physical events. One modern vision of the possible separation of mind and body is the "three-world" formulation of Popper. Cartesian dualism and Popper's three worlds are two forms of what is called epistemological pluralism, that is the notion that different epistemological methodologies are necessary to attain a full description of the world. Other forms of epistemological pluralist dualism include psychophysical parallelism and epiphenomenalism. Epistemological pluralism is one view in which the mind-body problem is not reducible to the concepts of the natural sciences.

A contrasting approach is called physicalism. Physicalism is a philosophical theory holding that everything that exists is no more extensive than its physical properties; that is, that there are no non-physical substances (for example physically independent minds). Physicalism can be reductive or non-reductive. Reductive physicalism is grounded in the idea that everything in the world can actually be reduced analytically to its fundamental physical, or material, basis. Alternatively, non-reductive physicalism asserts that mental properties form a separate ontological class to physical properties: that mental states (such as qualia) are not ontologically reducible to physical states. Although one might suppose that mental states and neurological states are different in kind, that does not rule out the possibility that mental states are correlated with neurological states. In one such construction, anomalous monism, mental events supervene on physical events, describing the emergence of mental properties correlated with physical properties – implying causal reducibility. Non-reductive physicalism is therefore often categorised as property dualism rather than monism, yet other types of property dualism do not adhere to the causal reducibility of mental states (see epiphenomenalism).

Incompatibilism requires a distinction between the mental and the physical, being a commentary on the incompatibility of (determined) physical reality and one's presumably distinct experience of will. Secondarily, metaphysical libertarian free will must assert influence on physical reality, and where mind is responsible for such influence (as opposed to ordinary system randomness), it must be distinct from body to accomplish this. Both substance and property dualism offer such a distinction, and those particular models thereof that are not causally inert with respect to the physical world provide a basis for illustrating incompatibilist free will (i.e. interactionalist dualism and non-reductive physicalism).

It has been noted that the laws of physics have yet to resolve the hard problem of consciousness: "Solving the hard problem of consciousness involves determining how physiological processes such as ions flowing across the nerve membrane cause us to have experiences." According to some, "Intricately related to the hard problem of consciousness, the hard problem of free will represents the core problem of conscious free will: Does conscious volition impact the material world?" Others however argue that " consciousness plays a far smaller role in human life than Western culture has tended to believe."
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