Soul, Mind, and Brain

This chapter adumbrates a Thomistic, non-Cartesian version of dualism, defending the Thomistic theory from the familiar charge of inconsistency by showing how it is possible to assert simultaneously that the human being is a single, unitary substance, that the soul is the 'form' of the human body, and yet that the soul can exist without the body by virtue of being an immaterial particular. It demonstrates that a Thomistic 'form' need not be a mere state of a thing, like a shape: it may also be an immaterial particular, present in every part of a substance, that causes it be in a certain state (such as that of being alive). Aquinas's view of the embodied souls avoids being dualistic by denying that the human body is a separable substance in its own right. What combines with the soul to produce a substantial human thing is not one thing but a plurality. Moreover, the chapter explains that Aquinas's claim that human thought has no bodily 'organ' does not entail the natural independence of our cognitive functions from the physical condition of the brain. It does, however, imply that mental content cannot be fully and determinately encoded in the brain's physical condition. Finally, the chapter clarifies the sense in which the disembodied soul is not for Aquinas (unlike Descartes) a substance.