An Introduction to Epistemology
Plato’s Theaetetus heralds the start of almost 25 centuries of heated philosophical debates about the nature of knowledge. Oversimplifying a bit, the dialogue successively considers the analyses of knowledge as perceptual, true, and justified true belief. It will likely not satisfy readers because all three conceptions are found wanting. Nevertheless, it’s very rich and exhibits all the great features of Platonic dialogues, especially Socrates’ insightful cleverness, making him raise deep questions about and powerful objections to the conceptions and views being considered. For instance, against Protagoras’ famous relativist statement that “man is the measure of all things,” Socrates develops his turning-around or reversal argument: relativism is only intelligible if it excludes non-relativism, but the exclusion of non-relativism boils down to the denial of relativism.
Although the substantive points are very interesting and important, Platonic dialogues in general and the Theaetetus in particular also pave the way methodologically. They pioneer the use of imaginary cases or “thought experiments” in testing philosophical conceptions and theories. Instead of restricting one’s attention to real-world examples and counterexamples in all their complexity, philosophical methodology allows and even recommends using one’s imagination, especially in inquiring what the nature or essence of a philosophically relevant phenomenon like “knowledge” really is. For in- stance, the second part of the Theaetetus is settled with a relatively straightforward counterexample to the conception of knowledge as true belief: an imaginary jury passing an accidentally true judgment about the guilt of someone accused of theft, based only on hearsay. It would be counter-intuitive to say that this jury knows that the accused is guilty of theft.