Plato and the Sophists: Eristic Practice, Cognition, and Perception

This dissertation traces metaphysical, epistemological and cognitive developments in Plato's canon from his earlier Euthydemus and Charmides to his great work on epistemology, the Theaetetus. I argue that Plato's confrontation with eristic (the methodology of his philosophical predecessors, the sophists) presents him with a serious epistemological challenge that can only be met through the development of a philosophical theory of cognition and perception. I also argue that the Theaetetus only appears to be an aporetic dialogue; read in the context of Plato's earlier work, it actually offers a series of refutations aimed at the theoretical assumptions that underpin the practice of sophistic eristic. I conclude by suggesting that the results of the Theaetetus ' arguments make possible his mature metaphysical and linguistic theory offered in the Sophist.;Chapter one begins by discussing the changes in the Greek view of the mind between Homer and Plato. Chapter two concerns Plato's early dialogue the Euthydemus. In the Euthydemus, I contend, the sophists Euthydemus and Dionysodorus assume what I call "the eristic theory," a set of metaphysical, epistemological and linguistic claims that underwrite the practice of sophistic refutation. It is usually assumed that sophistic eristic is constituted solely by the clever use of fallacy to persuade rather than logically convince. While I agree that clever use of fallacy is important, I argue that sophistic eristic is also constituted by challenging theoretical commitments. These commitments together entail epistemological infallibilism, a view that in the Euthydemus Socrates, I also argue, fails to refute. In chapter three I argue that all of the interlocutors of the Charmides assume both a broad perceptual model of introspection and the functional identity of all cognitive processes. I further argue that these assumptions account for some of the epistemological puzzles of that dialogue that Socrates cannot solve.;In the final chapter I make the case that in the Theaetetus Plato both explicitly and implicitly challenges the sophistic theory of the Euthydemus and the perceptual/cognitive model of the Charmides . I conclude that while the Theaetetus ends in apparent failure to define knowledge, we see that philosophical progress is made in the refutation of the theory that underpins sophistic eristic and of a deficient theory of cognition, perception and introspection. This refutation clears the way for Plato to develop a more philosophically promising model of human cognition and lanaguage.