Socrates: Then do we not come back to the old difficulty? For he who makes such a mistake does think one thing which he knows to be another thing which he knows; but this, as we said, was impossible, and afforded an irresistible proof of the nonexistence of false opinion, because otherwise the same person would inevitably know and not know the same thing at the same time.
Theaetetus: Most true.
Socrates: Then false opinion cannot be explained as a confusion of thought and sense, for in that case we could not have been mistaken about pure conceptions of thought; and thus we are obliged to say, either that false opinion does not exist, or that a man may not know that which he knows;—which alternative do you prefer?
Theaetetus: It is hard to determine, Socrates.
Socrates: And yet the argument will scarcely admit of both. But, as we are at our wits’ end, suppose that we do a shameless thing?
Theaetetus: What is it?
Socrates: Let us attempt to explain the verb “to know.”
Theaetetus: And why should that be shameless?
Socrates: You seem not to be aware that the whole of our discussion from the very beginning has been a search after knowledge, of which we are assumed not to know the nature.
Theaetetus: Nay, but I am well aware.
Socrates: And is it not shameless when we do not know what knowledge is, to be explaining the verb “to know”? The truth is, Theaetetus, that we have long been infected with logical impurity. Thousands of times have we repeated the words “we know,” and “do not know,” and “we have or have not science or knowledge,” as if we could understand what we are saying to one another, so long as we remain ignorant about knowledge; and at this moment we are using the words “we understand,” “we are ignorant,” as though we could still employ them when deprived of knowledge or science.
Theaetetus: But if you avoid these expressions, Socrates, how will you ever argue at all?
Socrates: I could not, being the man I am. The case would be different if I were a true hero of dialectic: and O that such an one were present! for he would have told us to avoid the use of these terms; at the same time he would not have spared in you and me the faults which I have noted. But, seeing that we are no great wits, shall I venture to say what knowing is? for I think that the attempt may be worth making.
Theaetetus: Then by all means venture, and no one shall find fault with you for using the forbidden terms.
Socrates: You have heard the common explanation of the verb “to know”?
Theaetetus: I think so, but I do not remember it at the moment.
Socrates: They explain the word “to know” as meaning “to have knowledge.”
Theaetetus: True.
Socrates: I should like to make a slight change, and say “to possess” knowledge.
Theaetetus: How do the two expressions differ?
Socrates: Perhaps there may be no difference; but still I should like you to hear my view, that you may help me to test it.
Theaetetus: I will, if I can.
Socrates: I should distinguish “having” from “possessing”: for example, a man may buy and keep under his control a garment which he does not wear; and then we should say, not that he has, but that he possesses the garment.
Theaetetus: It would be the correct expression.
Socrates: Well, may not a man “possess” and yet not “have” knowledge in the sense of which I am speaking? As you may suppose a man to have caught wild birds—doves or any other birds—and to be keeping them in an aviary which he has constructed at home; we might say of him in one sense, that he always has them because he possesses them, might we not?