Socrates at this point refers back to what was previously discussed. During this earlier discussion Theaetetus claimed that the essence of knowledge consists in perception. From this we conclude that the leading question of the conversation is: τί ἐστιν ἐπιστήμη; what is 'knowledge'? Socrates put this question forward quite clearly at the beginning of the dialogue (146 c 3), challenging Theaetetus as follows:

ἀλλ᾽ εὖ καὶ γενναίως εἰπέ: τί σοι δοκεῖ εἶναι ἐπιστήμη;

'So tell me frankly: what does that seem to you to be, "knowledge"?'

In the course of the conversation (151 e) Theaetetus arrives at his answer: the essence of knowledge is αἴσθησις, 'perception' [Wahrnehmung], as we shall provisionally translate it. The correctness or otherwise of Theaetetus' answer is then considered. At the moment we begin to listen in, this question takes a new and positive turn.

As auditors - genuine auditors, i.e. co-questioners - we allow ourselves to be drawn into the question 'what is knowledge?' A peculiar and at bottom eccentric question. What 'knowledge' is might be of interest to scholars, but even scholars will not direct their primary interest to such a question, nor will they take it very seriously. On the contrary, they will apply themselves to particular knowledge in particular domains, in order to gain an overall view and command of these domains. But what knowledge is as such is a quite empty question. Now the philosophers (especially those representing contemporary philosophy) will admit that it does appear this way, but will nonetheless insist that precisely this is the authentically philosophical question! For what is the difference between this science of philosophy and the other sciences? The sciences have divided up all beings among themselves. They have divided up the individual domains of the knowable for the purpose of their research. No specific domain is left over for philosophy. Yet one thing does remain for it to do: to inquire into knowledge as such, into the possibility of knowledge in general, and this means, for them, to inquire into the possibility of science as such. What knowledge is as such is the province of theory of science, whose most general task is sought in theory of knowledge. Accordingly, the question posed by Plato in the Theaetetus must be the fundamental question of the theory of knowledge, and so it comes about, particularly in the modern period, that the Theaetetus is commonly characterized as Plato's main epistemological dialogue. One sings the praises of Plato and the Greeks because they were already sufficiently advanced as to pose

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