Theaetetus (199)

SOC. But shall we say that he is going to read or count that which he does not know, when we have granted that he knows all letters and all numbers?

THEAET. But that too is absurd.

SOC. Shall we then say that words are nothing to us, if it amuses anyone to drag the expressions know and learn one way and another, but since we set up the distinction that it is one thing to possess knowledge and another thing to have it, we affirm that it is impossible not to possess what one possesses, so that it never happens that a man does not know that which he knows, but that it is possible to conceive a false opinion about it? For it is possible to have not the knowledge of this thing, but some other knowledge instead, when in hunting for some one kind of knowledge, as the various kinds fly about, he makes a mistake and catches one instead of another; so in one example he thought eleven was twelve, because he caught the knowledge of twelve, which was within him, instead of that of eleven, caught a ringdove, as it were, instead of a pigeon.

THEAET. Yes, that is reasonable.

SOC. But when he catches the knowledge he intends to catch, he is not deceived and has true opinion, and so true and false opinion exist and none of the things which formerly annoyed us interferes? Perhaps you will agree to this; or what will you do?

THEAET. I will agree.

SOC. Yes, for we have got rid of our difficulty about men not knowing that which they know; for we no longer find ourselves not possessing that which we possess, whether we are deceived about anything or not. However, another more dreadful disaster seems to be coming in sight.

THEAET. What disaster?

SOC. If the interchange of kinds of knowledge should ever turn out to be false opinion.

THEAET. How so?

SOC. Is it not the height of absurdity, in the first place for one who has knowledge of something to be ignorant of this very thing, not through ignorance but through his knowledge; secondly, for him to be of opinion that this thing is something else and something else is this thing—for the soul, when knowledge has come to it, to know nothing and be ignorant of all things? For by this argument there is nothing to prevent ignorance from coming to us and making us know something and blindness from making us see, if knowledge is ever to make us ignorant.

THEAET. Perhaps, Socrates, we were not right in making the birds represent kinds of knowledge only, but we ought to have imagined kinds of ignorance also flying about in the soul with the others; then the hunter would catch sometimes knowledge and sometimes ignorance of the same thing, and through the ignorance he would have false, but through the knowledge true opinion.