Abstract

The point of this project is to examine the grounds for choosing between Plato and Aristotle's ontologies, grounds which will not degenerate simply into one side claiming that abstract objects could exist without any instantiations, and the other side denying this. ;To get to this point, I investigate how Plato and Aristotle treat and use necessity de re. This is something fundamental to each of their ontologies and epistemologies, for it is their use of necessity which allows them to cross the river of Heracleitean flux. Examined in detail are various candidates proposed by interpreters for how Plato can argue that sensible particulars are not knowable. After finding these accounts deficient, I propose an account using the KK principle to prevent the unstable particulars from being known. ;Then I examine Aristotle's use of stability in his response to the Heracleitean skeptic. In the course of this examination, I try to clear up how several of Aristotle's ontological tools are related, like form, universal, quality, ousia, individual, essence, nature, belonging in itself, belonging accidentally, alteration, and coming to be. ;I then characterize the similarities and differences between Plato's and Aristotle's versions of essentialism. Where Plato's essences are eternal and are specified by how the Form is externally related to other Forms, Aristotle's are conditional on the existence of certain particulars and are in an important way internal to, or built into, the particulars. ;This characterization is then used as the basis for arguing for the superiority of Plato's scheme. It is held that intuitive feelings that Aristotle's theory is more sympathetic than Plato's to scientific enterprise are groundless, and that the theory of direct reference does not at all favor Aristotelian essentialism. In fact, I argue, Plato's ontology is favored by a particular version of an argument from parsimony, by considerations from contemporary biology, and by taking science as the discovery of scientific laws involving the external correlation of magnitudes