Man = Body + Soul
Aquinas's Arithmetic of Human Nature
For philosophers who find both a dualistic and a purely materialistic account of the human soul unacceptable, the Aristotelian-Thomistic conception of the soul as the substantial form of the living body may appear to be an intriguing alternative. However, even if one is not afraid of the prospect of committing oneself to an apparently “obsolete” metaphysics, developing such a commitment may not look to be a wise move after all, since upon closer inspection the doctrine may seem to be frustratingly obscure, if not directly self-contradictory.
In what follows I first present what may seem to be a fundamental problem of Aquinas's conception. Second, I will provide the solution that emerges from some crucial distinctions made by Aquinas in this context. The subsequent analysis of these distinctions will show how they fit into the larger context of Aquinas's general metaphysical, mereological and logical considerations, providing further clues as to how these considerations fit together in Aquinas's thought. In the concluding section I will argue that with the proper understanding of these conceptual connections, despite possible appearances to the contrary, Aquinas's conception does indeed offer a viable alternative to the modern dilemma of dualism vs. materialism.
In his book Aquinas on Mind, Anthony Kenny calls our attention to the problem as follows:
If we identify the human soul with Aristotelian substantial form, it is natural to identify the human body with prime matter. But body and soul are not at all the same pair of items as matter and form. This is a point