Abstract

Although the term ontology is absent from Plato’s works, his thinking undoubtedly belongs to the prehistory of this discipline. In his dialogues, one finds many observations concerning what exists and how it exists. Plato’s metaphysics is based on the fundamental distinction between two kinds of entities, namely intelligible forms and sensible particulars. This diairesis is presented in different but all compatible ways. The ontological difference between forms and sensible objects implies a causal priority: according to Plato, this priority corresponds to the proteron-hysteron scheme mentioned by Aristotle. The last part of the essay is devoted to the idea of the good and the problems related to its ontological status.