Definitions of knowledge have eluded philosophers since before Plato’s Theaetetus.
|“The official conclusion of the Theaetetus is that we still do not know how to define knowledge. Even on the most sceptical reading, this is not to say that we have not learned anything about what knowledge is like. As Theaetetus says (210b5), he has given birth to far more than he had in him.
And as many interpreters have seen, there may be much more to the ending than that. It may even be that, in the last two pages of the Theaetetus, we have seen hints of Plato’s own answer to the puzzle. Perhaps understanding has emerged from the last discussion, as wisdom did from 145d-e, as the key ingredient without which no true beliefs alone can even begin to look like they might count as knowledge. Perhaps it is only when we, the readers, understand this point—that epistemological success in the last resort depends on having epistemological virtue—that we begin not only to have true beliefs about what knowledge is, but to understand knowledge.
Theaetetus’ third definition of knowledge is ‘true belief with an account (meta logou alêthê doxan)’. In this sense, knowledge is a qualified belief. You can believe something that is (in fact) false, but you can not know something that is false. We know what we think we know, and our thinking can turn out to be incorrect, in which case it turns out that we did not know it, we believed it. Believing something that is untrue is false belief. It is absurd to say that we know something that is (unknowingly to us) in fact untrue. There is false belief, but not false knowledge; false knowledge turns out to be false belief. We do not know which of our knowledge we will consider to be false belief in the future. Furthermore, we do not know which of our knowledge is in fact just a false belief that we will never identify as such.
Socrates ends the Thaeatetus with a rejection of all the definitions of knowledge that were offered, including the true belief with rationalization, since rationalization is a type of knowledge about the uniqueness or composition of something, making the definition circular (knowledge is true belief plus knowledge). The exercise was not in vain, however, since it is better to admit than to pretend to know something that is not known, like the definition of knowledge.
[Photomedia Forum post by T.Neugebauer from Jan 1, 2007]