Veja também: Coletânea de excertos da obra completa de Platão, na tradução de Jowett, indexados por termos relevantes

Soc. And you allow and maintain that true opinion, combined with definition or rational explanation, is knowledge ?

Theaet. Exactly.

Soc. Then may we assume, Theaetetus, that to-day, and in this casual manner, we have found a truth which in former times many wise men have grown old and have not found ?

Theaet. At any rate, Socrates, I am satisfied with the present statement.

Soc. Which is probably correct — for how can there be knowledge apart from definition and true opinion ? And yet there is one point in what has been said which does not quite satisfy me.

Theaet. What was it ?

Soc. What might seem to be the most ingenious notion of all : — That the elements or letters are unknown, but the combination or syllables known.

Theaet. And was that wrong ?

Soc. We shall soon know ; for we have as hostages the instances which the author of the argument himself used.

Theaet. What hostages ?

Soc. The letters, which are the clements ; and the syllables, which are the combinations ; — he reasoned, did he not, from the letters of the alphabet ?

Theaet. Yes ; he did.

Soc. Let us take them and put them to the test, or rather, test ourselves : — What was the way in which we learned letters ? and, first of all, are we right in saying that syllables have a definition, but that letters have no definition ?

Theaet. I think so.

Soc. I think so too ; for, suppose that some one asks you to spell the first syllable of my name : — Theaetetus, he says, what is SO ?

Theaet. I should reply S and O.

Soc. That is the definition which you would give of the syllable ?

Theaet. I should.

Soc. I wish that you would give me a similar definition of the S.

Theaet. But how can any one, Socrates, tell the elements of an element ? I can only reply, that S is a consonant, a mere noise, as of the tongue hissing ; B, and most other letters, again, are neither vowel-sounds nor noises. Thus letters may be most truly said to be undefined ; for even the most distinct of them, which are the seven vowels, have a sound only, but no definition at all.

Soc. Then, I suppose, my friend, that we have been so far right in our idea about knowledge ?

Theaet. Yes ; I think that we have.

Soc. Well, but have we been right in maintaining that the syllables can be known, but not the letters ?

Theaet. I think so.

Soc. And do we mean by a syllable two letters, or if there are more, all of them, or a single idea which arises out of the combination of them ?

Theaet. I should say that we mean all the letters.

Soc. Take the case of the two letters S and O, which form the first syllable of my own name ; must not he who knows the syllable, know both of them ?

Theaet. Certainly.

Soc. He knows, that is, the S and O ?

Theaet. Yes.

Soc. But can he be ignorant of either singly and yet know both together ?

Theaet. Such a supposition, Socrates, is monstrous and unmeaning.

Soc. But if he cannot know both without knowing each, then if he is ever to know the syllable, he must know the letters first ; and thus the fine theory has again taken wings and departed.

Theaet. Yes, with wonderful celerity.