Theaetetus replies, that knowledge is what he learns of Theodorus, i.e. geometry and arithmetic; and that there are other kinds of knowledge—shoemaking, carpentering, and the like. But Socrates rejoins, that this answer contains too much and also too little. For although Theaetetus has enumerated several kinds of knowledge, he has not explained the common nature of them; as if he had been asked, “What is clay?” and instead of saying “Clay is moistened earth,” he had answered, “There is one clay of image-makers, another of potters, another of oven-makers.” Theaetetus at once divines that Socrates means him to extend to all kinds of knowledge the same process of generalization which he has already learned to apply to arithmetic. For he has discovered a division of numbers into square numbers, 4, 9, 16, etc., which are composed of equal factors, and represent figures which have equal sides, and oblong numbers, 3, 5, 6, 7, etc., which are composed of unequal factors, and represent figures which have unequal sides. But he has never succeeded in attaining a similar conception of knowledge, though he has often tried; and, when this and similar questions were brought to him from Socrates, has been sorely distressed by them. Socrates explains to him that he is in labour. For men as well as women have pangs of labour; and both at times require the assistance of midwives. And he, Socrates, is a midwife, although this is a secret; he has inherited the art from his mother bold and bluff, and he ushers into light, not children, but the thoughts of men. Like the midwives, who are “past bearing children,” he too can have no offspring—the God will not allow him to bring anything into the world of his own. He also reminds Theaetetus that the midwives are or ought to be the only matchmakers (this is the preparation for a biting jest, 151 B); for those who reap the fruit are most likely to know on what soil the plants will grow. But respectable midwives avoid this department of practice—they do not want to be called procuresses. There are some other differences between the two sorts of pregnancy. For women do not bring into the world at one time real children and at another time idols which are with difficulty distinguished from them. “At first,” says Socrates in his character of the man-midwife, “my patients are barren and stolid, but after a while they ’round apace,’ if the gods are propitious to them; and this is due not to me but to themselves; I and the god only assist in bringing their ideas to the birth. Many of them have left me too soon, and the result has been that they have produced abortions; or when I have delivered them of children they have lost them by an ill bringing up, and have ended by seeing themselves, as others see them, to be great fools. Aristides, the son of Lysimachus, is one of these, and there have been others. The truants often return to me and beg to be taken back; and then, if my familiar allows me, which is not always the case, I receive them, and they begin to grow again. There come to me also those who have nothing in them, and have no need of my art; and I am their matchmaker (see above), and marry them to Prodicus or some other inspired sage who is likely to suit them. I tell you this long story because I suspect that you are in labour. Come then to me, who am a midwife, and the son of a midwife, and I will deliver you. And do not bite me, as the women do, if I abstract your firstborn; for I am acting out of goodwill towards you; the God who is within me is the friend of man, though he will not allow me to dissemble the truth. Once more then, Theaetetus, I repeat my old question—‘What is knowledge?’ Take courage, and by the help of God you will discover an answer.” “My answer is, that knowledge is perception.” “That is the theory of Protagoras, who has another way of expressing the same thing when he says, ‘Man is the measure of all things.’ He was a very wise man, and we should try to understand him. In order to illustrate his meaning let me suppose that there is the same wind blowing in our faces, and one of us may be hot and the other cold. How is this? Protagoras will reply that the wind is hot to him who is cold, cold to him who is hot. And ‘is’ means ‘appears,’ and when you say ‘appears to him,’ that means ‘he feels.’ Thus feeling, appearance, perception, coincide with being. I suspect, however, that this was only a ‘façon de parler,’ by which he imposed on the common herd like you and me; he told ‘the truth’ (in allusion to the title of his book, which was called ‘The Truth’) in secret to his disciples. For he was really a votary of that famous philosophy in which all things are said to be relative; nothing is great or small, or heavy or light, or one, but all is in motion and mixture and transition and flux and generation, not ‘being,’ as we ignorantly affirm, but ‘becoming.’ This has been the doctrine, not of Protagoras only, but of all philosophers,
