Question: Why is Plato concerned about the difference between mere belief and true knowledge, particularly concerning the issues of justice? How does that affect his view of rhetoric?

Whether or not Plato is aware of this, his aristocratic position is threatened by rhetoric in a court of law. Law of that day was usually based on knowledge–a knowledge that kept these rich white men in power for so long. But along comes rhetoric with its power to convince people of an argument with belief instead. Now the knowledge of that day relied heavily on endoxa, but an argument of belief could pull on the heartstrings of an individual, separating them from “common sense” and offering them a different alternative in an environment where such thought is easy to encourage (when actively listening to a good speaker it’s easy to get caught up in the emotion; it takes conscious effort to remain separate from the rhetoric and critically analyze a speech). For example, I could provide facts and figures showing how oil spills actually improve people’s health (bare with me, I’m arguing a crazy point). However, even if it wasn’t true, I can talk about a little child watching his parents’ eyes boil out of their skulls because of oil skills…which one argument would be believed, regardless of which was true.

It’s because of this that Plato despises rhetoric. He sees it as a means to empower the masses and shatter the traditional regime. When Gorgias finally snaps with Socrates in Plato’s Gorgias, he puts in relatively plain words what Plato fears most from rhetoric and its practitioners: “he can persuade the multitude better than any other man of anything which he pleases (150).”