Knowledge
Plato's dialogue surrounds a conversation between Socrates and a student named Theaetetus, wherein Socrates urges Theaetetus to define "knowledge." Throughout the conversation, Socrates asks Theaetetus questions to make him reconsider and refine his definitions. For example, at the beginning of the dialogue, Socrates asks if knowledge and wisdom are the same thing, which Theaetetus affirms. After some prompting, however, Theaetetus changes his mind.
Truth
Socrates spends a good portion of the dialogue discussing Protagoras' statement that "Man is the measure of all things," a statement which gives credibility to everyone's individual opinions. This is known as relativism. Theaetetus agrees that every individual's truths (or, opinions) are relative to themselves, but Socrates makes him second guess his agreement with Protagoras. Socrates rebuts Protagoras' claim by pointing out that even though everyone holds different opinions, that does not mean that every single opinion is correct, or true.
Learning and Teaching
Learning and teaching is a major theme of Theaetetus. Theaetetus expects Socrates to be his teacher in figuring out what knowledge is, but Socrates tells him that he "is sterile in the point of wisdom," and his job is to help Theaetetus "give birth" to his own wisdom. However, in this way, Socrates still acts as Theaetetus' teacher: he guides him and helps him discover his own knowledge. Though Socrates is not teaching Theaetetus the answer of what knowledge is, he is still teaching him how to find the answer. Similarly, Theaetetus acts as Socrates' teacher by figuring out what knowledge is. Both Theaetetus and Socrates are simultaneously each others' teachers and students, demonstrating the fluidity and interconnectedness of these roles.
