Abstract

Socrates and Plato are one in species, but diverse in number. What accounts for their diversity in this sense? This question lies at the center of a longstanding controversy over what has been called the principle of individuation. Though multiple questions have been investigated using the terminology of individuation, the author’s focus here is on the question of what, for Aristotle, explains the numerical diversification of cospecific organisms, along with the two mainstream answers to this question: that their diversity derives from the diversity of their matter, or that it derives from the diversity of their forms. She argues that if we take Aristotle’s metaontology as our starting point for investigating this question, both of the mainstream views falter for the same reason. Aristotle’s analyses of the concepts of unity and diversity support the conclusion that the diversity of cospecific organisms is underived.