All this confusion arises out of our attempt to explain false opinion without having explained knowledge. What then is knowledge? Theaetetus repeats that knowledge is true opinion. But this seems to be refuted by the instance of orators and judges. For surely the orator cannot convey a true knowledge of crimes at which the judges were not present; he can only persuade them, and the judge may form a true opinion and truly judge. But if true opinion were knowledge they could not have judged without knowledge.
Once more. Theaetetus offers a definition which he has heard: Knowledge is true opinion accompanied by definition or explanation. Socrates has had a similar dream, and has further heard that the first elements are names only, and that definition or explanation begins when they are combined; the letters are unknown, the syllables or combinations are known. But this new hypothesis when tested by the letters of the alphabet is found to break down. The first syllable of Socrates’ name is So. But what is So? Two letters, s and o, a sibilant and a vowel, of which no further explanation can be given. And how can anyone be ignorant of either of them, and yet know both of them? There is, however, another alternative:—We may suppose that the syllable has a separate form or idea distinct from the letters or parts. The all of the parts may not be the whole. Theaetetus is very much inclined to adopt this suggestion, but when interrogated by Socrates he is unable to draw any distinction between the whole and all the parts. And if the syllables have no parts, then they are those original elements of which there is no explanation. But how can the syllable be known if the letter remains unknown? In learning to read as children, we are first taught the letters and then the syllables. And in music, the notes, which are the letters, have a much more distinct meaning to us than the combination of them.
Once more, then, we must ask the meaning of the statement, that “Knowledge is right opinion, accompanied by explanation or definition.” Explanation may mean, (1) the reflection or expression of a man’s thoughts—but every man who is not deaf and dumb is able to express his thoughts—or (2) the enumeration of the elements of which anything is composed. A man may have a true opinion about a wagon, but then, and then only, has he knowledge of a wagon when he is able to enumerate the hundred planks of Hesiod. Or he may know the syllables of the name Theaetetus, but not the letters; yet not until he knows both can he be said to have knowledge as well as opinion. But on the other hand he may know the syllable “The” in the name Theaetetus, yet he may be mistaken about the same syllable in the name Theodorus, and in learning to read we often make such mistakes. And even if he could write out all the letters and syllables of your name in order, still he would only have right opinion. Yet there may be a third meaning of the definition, besides the image or expression of the mind, and the enumeration of the elements, viz. (3) perception of difference.
For example, I may see a man who has eyes, nose, and mouth;—that will not distinguish him from any other man. Or he may have a snub-nose and prominent eyes;—that will not distinguish him from myself and you and others who are like me. But when I see a certain kind of snub-nosedness, then I recognize Theaetetus. And having this sign of difference, I have knowledge. But have I knowledge or opinion of this difference; if I have only opinion I have not knowledge; if I have knowledge we assume a disputed term; for knowledge will have to be defined as right opinion with knowledge of difference.
And so, Theaetetus, knowledge is neither perception nor true opinion, nor yet definition accompanying true opinion. And I have shown that the children of your brain are not worth rearing. Are you still in labour, or have you brought all you have to say about knowledge to the birth? If you have any more thoughts, you will be the better for having got rid of these; or if you have none, you will be the better for not fancying that you know what you do not know. Observe the limits of my art, which, like my mother’s, is an art of midwifery; I do not pretend to compare with the good and wise of this and other ages.
And now I go to meet Meletus at the porch of the King Archon; but tomorrow I shall hope to see you again, Theodorus, at this place.
I. The saying of Theaetetus, that “Knowledge is sensible perception,” may be assumed to be a current philosophical opinion of the age. “The ancients,” as Aristotle (De Anima III 3) says, citing a verse of Empedocles, “affirmed knowledge to be the same as perception.” We may now examine these words, first, with reference to their place in the history of philosophy, and secondly, in relation to modern speculations.
(a) In the age of Socrates the mind was passing from the object to the subject. The same impulse which a century before had led men to form conceptions of the world, now led them to frame
