The Theaetetus is the first of seven dialogues chronologically leading up to the death of Socrates. It is an extraordinarily unique dialogue in the Platonic corpus.
At the outset, the dialogue is framed as a conversation between Euclides and Terpsion from Megara around three decades after the initial conversation between Socrates and Theaetetus had originally taken place (When Theaetetus was fifteen years old). Recall a similar framing of the narrative used in the Symposium. The dialogue is unique in that Euclides claims to have confirmed its contents with Socrates during the troubled time of his trial, making it the closest dialogue in existence to have been written by Socrates (the Republic is also debatable).
At any rate, both of the men, Euclides and Terpsion, had heard of Theaetetus, renowned for his bravery and patriotism, as evidenced by his decision upon being wounded at Corinth to travel back to Athens to die. The two tiresome and weary Megarans listen the dialogue as if it were a relic, hand copied exactly as it happened. Theaetetus was also well known for his geometric demonstrations. Why do we have a dialogue focusing on Theaetetus? Why does it not focus on Theodorus, for example?
Nothing is accidental in a Platonic dialogue, and the decision to focus the title, as well as much of the content on the character of Theaetetus is not excused from this principle. Theaetetus is a young man of fifteen when speaking with Socrates, and like many other young men he is taken in by the works of Protagoras and the geometry of Theodorus of Corinth. In a word, he is impressionable. He is a well-born man, but lamentably, his guardians have wasted much of his substance. At the start of the dialogue he is willing and eager and naive, but by the close we find vague traces of rebelliosness -a danger that is exposed in the Socratic dialectic.
Their conversation is focused on the question of knowledge (episteme) -what is it? Theaetetus attempts to defend the Protagorean position that knowledge is nothing other than perception (he provides essentially three definitions that are proven to be false, and a fourth definition through the mouth of Socrates that is also proven to be insufficient). Each definition is found inadequate on the grounds that knowledge is being and other things like opinions or perceptions are relative, or in a state of becoming.
To step back for a moment, recall Socrates’s reluctant exchange in the Protagoras in which Socrates defends the notion that virtue is knowledge and that it cannot be taught, while Protagoras claims that virtue is not knowledge but that is can be taught (he also claims to be its teacher). If virtue cannot be taught and it is instead something innate or genetic, what does that mean for the sustainability of the city? Enter the need for the natural hierarchy of people found in the Republic during the formation of Kallipoli, in which their are three races of people: gold, silver, and bronze (borrowed from earlier Hesiodic writings). The gold are the high-born, naturally superior, philosophic types. This hierarchy is meant to most closely match natural law is the result of a belief that virtue can be taught. However, other forms of government, like democracy, rely on a belief that virtue can be taught, as Jefferson once noted that the future of the republic relies on a virtuous citizenry. Socrates’s claims undermine this principle.
However, returning to the beginning with our initial question regarding Theaetetus, perhaps the prologue is again illuminating. Theaetetus is renowned outside of Athens for his bravery and courage, less so for his geometry. Others are perplexed about why he would choose to return to Athens while injured, instead of remaining in Corinth to properly heal and recover. It could have been a foolhardy thing to do, but the distinction between patriotism and foolhardiness is hazy. Patriotism is valued in the hearts of the broader citizenry. Therefore, his death in returning to Athens was to give Athens the greater glory. Is it possible that this story of an older Theaetetus is evidence that virtue is teachable? Could it be that his conversation with Socrates some thirty years prior had impressed upon him a sense of virtue? Although, if we maintain Socrates’s claim that virtue is knowledge, then we also find some success with Theaetetus for his work with irrational commensurates in Euclidean geometry.
In exploring this question with Theaetetus, Socrates is also famously examining himself since he claims to be devoid of knowledge -except in knowing what he does not know. In this way, Socrates actually has quite an extensive knowledge. However cannot be geometry, arithmetic, and the arts as these are all a “swarm” of examples, whereas Socrates is looking for the “hive” (Meno). Knowledge cannot be perception because then the madman, the dreamer, the healthy, the unhealthy, all will perceive things differently and each would be correct (relativism) rendering knowledge meaningless. Knowledge cannot be an impression as the images of the “wax” and the “birdcage” demonstrations. Lastly, knowledge cannot be true opinion nor true opinion with logos for then knowledge could at best, only be a guess, never certain, and has been stated previously Socrates is in search of being, not becoming.
Ultimately, the dialogue concludes not with a sufficient definition of knowledge, but rather with an eye toward the good the conversation has brought upon Theaetetus for it will make him more manly and courageous in the long run. The distinction between the form and the content is sharpened and the effectual truth of their discussion has been demonstrated with Theaetetus’s courage in battle at Corinth. The philosophic life is exemplified as best in the Theaetetus as it makes us more aware of our ignorance, but also fearful of it; and more aware of our finitude, but less burdened by it. In this way, the progress made in the dialogue is toward a better way of being for Theaetetus.