Raphael Mary Salzillo

The importance of the concept of subsistence for Thomas Aquinas' metaphysics, and especially for his account of human nature, cannot be overstated. Yet few authors have attempted to give a systematic explanation of what subsistence is, often glossing it in terms of the ability of a thing to exist independently. This is unfortunate since this standard gloss on the concept of subsistence is, as an interpretation of Aquinas, demonstrably mistaken. In this paper, I propose a more defensible account of subsistence by first specifying its extension correctly, and then moving to a positive, conceptual explication. In doing so, I take seriously what Aquinas says about the subsistence and operation of both complete substances and subsistent parts of substances, including bodily organs and the human soul.

This article gives an overview of the mereological thought of the medieval philosopher and theologian Saint Thomas Aquinas. Until the 20th century mereology—the study of the relationship of whole and part—was not generally recognized as a distinct domain of philosophy and so Aquinas, like most of his contemporaries, has no single systematic treatment of it as a topic in its own right. However, a cohesive account of part‐whole relations can be pieced together from the various metaphysical, ethical and theological contexts in which Aquinas deals with mereological issues. In this article, I give an account of both Aquinas's conceptual understanding of composition and his taxonomy of the different kinds of wholes and parts that there are. I end with comments on three marginal cases of mereological relationships in Aquinas's philosophy.