Abstract

Many late medieval Aristotelians assumed that a natural substance has several substantial forms in addition to matter as really distinct parts. This assumption gave rise to a unity problem: why is a substance more than a conglomeration of all these parts? This paper discusses Francisco Suárez’s answer. It first shows that he rejected the idea that there is a plurality of forms, emphasizing instead that each substance has a single form and hence a single structuring principle. It then examines his account of the relationship between matter and form. While accepting the thesis that these two parts are really distinct entities, he claimed that there is a special “mode of union” that binds them together. With this account, he defended the essential unity of a natural substance, but he transformed the program of Aristotelian metaphysics: not substances, but entities and modes inside them, are now the basic building blocks of reality.