Abstract

At the beginning of Categories 5, Aristotle distinguishes between two kinds of substance: primary substance and secondary substance. Primary substances include particular living organisms, inanimate objects, and their parts. Secondary substances are the species and genera of these. This distinction is unique to the Categories, which raises the question of why Aristotle treats species and genera as substances. I argue that Aristotle has two distinct reasons for doing so, and contrast my interpretation with recent alternatives. On my view, species and genera enjoy two kinds of fundamentality – ontological and epistemological – in virtue of which they warrant their status as substances.