The Socrates of the “Theaetetus” is the same as the Socrates of the earlier dialogues. He is the invincible disputant, now advanced in years, of the “Protagoras” and “Symposium”; he is still pursuing his divine mission, his “Herculean labours,” of which he has described the origin in the “Apology”; and he still hears the voice of his oracle, bidding him receive or not receive the truant souls. There he is supposed to have a mission to convict men of self-conceit; in the “Theaetetus” he has assigned to him by God the functions of a man-midwife, who delivers men of their thoughts, and under this character he is present throughout the dialogue. He is the true prophet who has an insight into the natures of men, and can divine their future (142 C); and he knows that sympathy is the secret power which unlocks their thoughts. The hit at Aristides, the son of Lysimachus, who was specially committed to his charge in the “Laches,” may be remarked by the way. The attempt to discover the definition of knowledge is in accordance with the character of Socrates as he is described in the Memorabilia, asking What is justice? what is temperance? and the like. But there is no reason to suppose that he would have analyzed the nature of perception, or traced the connection of Protagoras and Heracleitus, or have raised the difficulty respecting false opinion. The humorous illustrations, as well as the serious thoughts, run through the dialogue. The snub-nosedness of Theaetetus, a characteristic which he shares with Socrates, and the man-midwifery of Socrates, are not forgotten in the closing words. At the end of the dialogue, as in the Euthyphro, he is expecting to meet Meletus at the porch of the king Archon; but with the same indifference to the result which is everywhere displayed by him, he proposes that they shall reassemble on the following day at the same spot. The day comes, and in the “Sophist” the three friends again meet, but no further allusion is made to the trial, and the principal share in the argument is assigned, not to Socrates, but to an Eleatic stranger; the youthful Theaetetus also plays a different and less independent part. And there is no allusion in the Introduction to the second and third dialogues, which are afterwards appended. There seems, therefore, reason to think that there is a real change, both in the characters and in the design.
The dialogue is an enquiry into the nature of knowledge, which is interrupted by two digressions. The first is the digression about the midwives, which is also a leading thought or continuous image, like the wave in the Republic, appearing and reappearing at intervals. Again and again we are reminded that the successive conceptions of knowledge are extracted from Theaetetus, who in his turn truly declares that Socrates has got a great deal more out of him than ever was in him. Socrates is never weary of working out the image in humorous details—discerning the symptoms of labour, carrying the child round the hearth, fearing that Theaetetus will bite him, comparing his conceptions to wind-eggs, asserting an hereditary right to the occupation. There is also a serious side to the image, which is an apt similitude of the Socratic theory of education (compare Republic VII 518 D, “Sophist” 230), and accords with the ironical spirit in which the wisest of men delights to speak of himself.
The other digression is the famous contrast of the lawyer and philosopher. This is a sort of landing-place or break in the middle of the dialogue. At the commencement of a great discussion, the reflection naturally arises, How happy are they who, like the philosopher, have time for such discussions (compare Republic V 450)! There is no reason for the introduction of such a digression; nor is a reason always needed, any more than for the introduction of an episode in a poem, or of a topic in conversation. That which is given by Socrates is quite sufficient, viz. that the philosopher may talk and write as he pleases. But though not very closely connected, neither is the digression out of keeping with the rest of the dialogue. The philosopher naturally desires to pour forth the thoughts which are always present to him, and to discourse of the higher life. The idea of knowledge, although hard to be defined, is realised in the life of philosophy. And the contrast is the favourite antithesis between the world, in the various characters of sophist, lawyer, statesman, speaker, and the philosopher—between opinion and knowledge—between the conventional and the true.
The greater part of the dialogue is devoted to setting up and throwing down definitions of science and knowledge. Proceeding from the lower to the higher by three stages, in which perception, opinion, reasoning are successively examined, we first get rid of the confusion
