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Reading group: Plato’s Theaetetus, the three definitions of knowledge

Giulia Ferrante Fellow
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Knowledge & beliefGreek & RomanPlatonismLudwig WittgensteinPlatoSocrates#aviary#definition-of-knowledge#reading-group#theaetetus
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Every year I teach the Theaetetus to my liceo students in fragments, and every year I promise myself I'll read it whole again with adults. This is that promise.

It is the founding text of epistemology and also one of Plato's most frustrating dialogues: it tries three definitions of knowledge, demolishes all three, and ends without an answer. I think the ending is the point.

Translation: M. J. Levett, revised by Myles Burnyeat (Hackett), whose long introduction is a small book in itself. Any reliable translation with Stephanus numbers will do.

Plan (by Stephanus pages, roughly):

  • Weeks 1–2: the prologue and Socrates as midwife (to 151), then knowledge is perception and its tie to Protagoras's "man is the measure" (to about 187).
  • Week 3: knowledge is true judgement, including the puzzle of false belief, the wax tablet and the aviary (about 187–201).
  • Week 4: knowledge is true judgement with an account (logos), the "dream" theory of elements and complexes, and the collapse (201 to the end).

Post per week. I'm especially curious how people outside the Greek tradition read the problem.

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5 replies

  1. Henrike Vogel

    Fellow

    Weeks 1–2. I hadn't read the midwife passage since school. Socrates says he is barren of wisdom himself; he only helps others give birth and tests whether the child is real or a "wind-egg". That changes how you read the whole dialogue: the failed definitions are not Plato's failures, they're Theaetetus's wind-eggs, and the method of testing is what survives. As a retired teacher I recognised it painfully.

  2. Vikram Sethi

    Fellow

    Week 3. The aviary made me laugh, because the example Plato uses is arithmetic: someone who knows 7 and 5 and 11 and 12 can still judge that 7 + 5 = 11. He has all the birds in the cage and grabs the wrong one. Every mathematics teacher has watched this happen. The student "knows" the numbers and still errs. Plato's question, how can you misidentify something you know, is exactly what I see on exam scripts.

    Helpful · 1
  3. Meera Kulkarni

    Fellow

    Week 3, from the Nyāya side. What strikes me is that Plato tries to define knowledge by adding something to true belief. Nyāya instead defines a valid cognition by its source: perception, inference, comparison, testimony. A true cognition produced by a faulty source is not pramā in the full sense. So the Nyāya would ask Plato not "what must be added?" but "where did it come from?" In a way, that is reliabilism two thousand years early, though the comparison needs care.

    Helpful · 2
  4. Tomasz Szewczak

    Fellow

    Week 4. The "dream" theory is astonishing: the world is made of simple elements that can only be named, not explained, and complexes are known by spelling out their elements. Socrates then argues this makes the complexes knowable but the elements unknowable, which is absurd. Wittgenstein quotes this passage early in the Investigations, recognising his own earlier logical atomism in it. A twentieth-century philosopher finding his first book in a dialogue from the fourth century BCE is a good reason to read Plato.

    Helpful · 3
  5. Giulia Ferrante

    Fellow

    Week 4, and my own conclusion. Just before the third definition, Socrates gives the example of a jury persuaded by a skilled speaker to a true verdict about something only an eyewitness could know. They judge truly, but do not know. That case does more work than any of the definitions: it shows true belief is not enough and that how you came by it matters. Every later theory, including Meera's Nyāya, is an attempt to say what the jury lacked.