Abstract

The view that the soul can exist separately from the body is commonly associated with dualism. Since Plato’s Phaedo (Phd.) argues that the soul is immortal and survives the death of the body, there seems to be reason to call Plato, in that dialogue at least, a ‘dualist’. Yet, as we know, there are many kinds of dualism, so we have thereby not said very much. Let me therefore start with some distinctions. First of all, we can distinguish between two kinds of dualism which say that the soul is a different kind of substance from the body. On one version, call it ‘strong’ substance dualism, no properties of mind can also be properties of body. Mind is defined as a kind of thing that uniquely has a certain property or set of properties, say consciousness, just as body is defined by its unique properties, say spatial extension. This would seem to be Descartes’ view. On another version, call it ‘weak’ substance dualism, no essential or defining properties of mind are also properties of body. This leaves it open whether the mind and body may share some accidental or non-defining properties. Finally, there is an even weaker kind of dualism which we may call property dualism. According to this view, there are mental properties which are distinct from and irreducible to bodily properties.4 However, these mental properties may or not be properties of an underlying substance that also has bodily properties. In other words, the same thing may have both mental and bodily properties, so having mental properties is not enough to make something a different kind of substance.