Ἆρ᾽ οὖν ὁ τὰ ψευδῆ δοξάζων, ἃ οἶδε, ταῦτα οἴεται οὐ ταῦτα εἶναι ἀλλὰ ἕτερα ἄττα ὧν οἶδε,

'Someone thinks the things he knows are not these things, but some other things he knows.'

An example: someone knows Theaetetus and Socrates; in the distance he sees a man (who is actually Theaetetus) coming towards him along the street; he takes this man to be Socrates. On the present interpretation this means that he takes Theaetetus, whom he knows, as not he whom he knows (as approaching him along the street) but as someone else. He therefore holds what he knows for something he does not know. For otherwise he would have taken the man as Theaetetus rather than as Socrates. So the remarkable circumstance emerges that someone who knows both Socrates and Theaetetus in this case also and simultaneously does not know them (188 b 4 f.):

ἀμφότερα εἰδὼς ἀγνοεῖ αὖ ἀμφότερα;

'He knows both [he knows who Socrates is, and who Theaetetus is] and yet is ignorant of both.'

For, as we say, he confuses them.

In the case of a distorted view, one knows, and does not know, one and the same thing! However, Theaetetus promptly says that such a thing is impossible, ἀδύνατον. If this is so, what remains? One might presume: he knows neither. Then having a distorted view would mean that one takes something one does not know for something else one likewise does not know. Then someone who knew neither Theaetetus nor Socrates could intend both while taking Socrates for Theaetetus or Theaetetus for Socrates. That is obviously impossible! The distorted view, consequently, cannot exist at all. The guiding principle, and what followed from it, remain valid: it is impossible that someone who knows something also does not know it, and vice versa.

Socrates now (188 c 2) gives this result a different and characteristic turn: it is not the case that someone takes what he knows as something he does not know. Theaetetus answers: τέρας γὰρ ἔσται, 'that would be a miracle'.

To anticipate, and thus to make visible the astonishing structure of the whole: this miracle does in fact exist. Especially in his later dialogues, Plato always employs this expression τέρας, miracle, when something initially appears as absolutely impossible and miraculous to the common

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