Aquinas believes that the human soul is immortal. His principal argument for this conclusion, in 75.6, rests on the soul's unique status as a form that is also a substance (§12.1). But to establish that the soul continues to exist apart from its body, he needs to show that the soul continues to function apart from its body. Q89 is devoted to explaining how the intellect continues to function in this way (§12.2). But the fact that a separated intellect can continue to function does not show that the soul survives death, and so Aquinas has to explain how such an intellect can still be considered a human soul (§12.3). He then faces the further problem of explaining how a separated soul can serve to sustain the existence of the human being. In fact, Aquinas believes that a separated soul is not a human being; the human being ceases to exist at death, and will come back into existence only with the resurrection of the body. Reflection on this doctrine sheds light on how, for Aquinas, material substances preserve their identity over time (§12.4).

Incorruptibilis

All human beings surely hope for life after death. What we hope for, quite simply, is that we ourselves will continue to exist, in some reasonably pleasant venue. Although the hope can be simply stated, it is a philosophically complex matter to determine what would have to be the case to ensure such personal survival. This chapter explores Aquinas's account of these issues.