In philosophy of mind, dualism is the position that mental phenomena are, in some respects, non-

physical,[1] or that the mind and body are not identical.[2] Thus, it encompasses a set of views about

the relationship between mind and matter, and is contrasted with other positions, such

as physicalism, in the mind–body problem.[1][2]

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.[3][4] For Plato however, the soul was not dependent on the

physical body; he believed inmetempsychosis, the migration of the soul to a new physical body.[5]

Dualism is closely associated with the philosophy of René Descartes (1641), which holds that the

mind is a nonphysical substance. Descartes clearly identified the mind with consciousness and self-

awareness and distinguished this from the brain as the seat of intelligence.[6] Hence, he was the first

to formulate the mind–body problem in the form in which it exists today.[7] 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.

Types of mind–body dualism[edit]

Ontological dualism makes dual commitments about the nature of existence as it relates to mind and

matter, and can be divided into three different types:

1. Substance dualism asserts that mind and matter are fundamentally distinct kinds of

foundations.[1]

2. Property dualism suggests that the ontological distinction lies in the differences between

properties of mind and matter (as in emergentism).[1]

3. Predicate dualism claims the irreducibility of mental predicates to physical predicates.[1]

Cartesian dualism[edit]

Substance dualism is a type of dualism most famously defended by René Descartes, which states

that there are two kinds of foundation: mental and body.[6] This philosophy states that the mental can

exist outside of the body, and the body cannot think. Substance dualism is important historically for

having given rise to much thought regarding the famous mind–body problem. Substance dualism is

a philosophical position compatible with most theologies which claim that immortal souls occupy an

independent "realm" of existence distinct from that of the physical world.[1]

Property dualism[edit]

Main article: Property dualism

Property dualism asserts that an ontological distinction lies in the differences between properties of

mind and matter, and that consciousness is ontologically irreducible toneurobiology and physics. It

asserts that when matter is organized in the appropriate way (i.e., in the way that living human

bodies are organized), mental properties emerge. Hence, it is a sub-branch of emergent materialism.

What views properly fall under the property dualism rubric is itself a matter of dispute. There are

different versions of property dualism, some of which claim independent categorisation.[8]

Non-reductive physicalism is a form of property dualism in which it is asserted that all mental states

are causally reducible to physical states. One argument for this has been made in the form

of anomalous monism expressed by Donald Davidson, where it is argued that mental events are

identical to physical events, and there can be strict law-governed causal relationships. Another

argument for this has been expressed by John Searle, who is the advocate of a distinctive form of

physicalism he calls biological naturalism. His view is that although mental states are ontologically

irreducible to physical states, they are causally reducible (see causality). He has acknowledged that

"to many people" his views and those of property dualists look a lot alike. But he thinks the

comparison is misleading.[8]