THEAETETUS: Of course.
SOCRATES: And I who am the patient, and that which is the agent, will produce something different in each of the two cases?
THEAETETUS: Certainly.
SOCRATES: The wine which I drink when I am in health, appears sweet and pleasant to me?
THEAETETUS: True.
SOCRATES: For, as has been already acknowledged, the patient and agent meet together and produce sweetness and a perception of sweetness, which are in simultaneous motion, and the perception which comes from the patient makes the tongue percipient, and the quality of sweetness which arises out of and is moving about the wine, makes the wine both to be and to appear sweet to the healthy tongue.
THEAETETUS: Certainly; that has been already acknowledged.
SOCRATES: But when I am sick, the wine really acts upon another and a different person?
THEAETETUS: Yes.
SOCRATES: The combination of the draught of wine, and the Socrates who is sick, produces quite another result; which is the sensation of bitterness in the tongue, and the motion and creation of bitterness in and about the wine, which becomes not bitterness but something bitter; as I myself become not perception but percipient?
THEAETETUS: True.
SOCRATES: There is no other object of which I shall ever have the same perception, for another object would give another perception, and would make the percipient other and different; nor can that object which affects me, meeting another subject, produce the same, or become similar, for that too would produce another result from another subject, and become different.
THEAETETUS: True.
SOCRATES: Neither can I by myself, have this sensation, nor the object by itself, this quality.
THEAETETUS: Certainly not.
SOCRATES: When I perceive I must become percipient of something – there can be no such thing as perceiving and perceiving nothing; the object, whether it become sweet, bitter, or of any other quality, must have relation to a percipient; nothing can become sweet which is sweet to no one.
THEAETETUS: Certainly not.
SOCRATES: Then the inference is, that we (the agent and patient) are or become in relation to one another; there is a law which binds us one to the other, but not to any other existence, nor each of us to himself; and therefore we can only be bound to one another; so that whether a person says that a thing is or becomes, he must say that it is or becomes to or of or in relation to something else; but he must not say or allow any one else to say that anything is or becomes absolutely: – such is our conclusion.
THEAETETUS: Very true, Socrates.
SOCRATES: Then, if that which acts upon me has relation to me and to no other, I and no other am the percipient of it?
THEAETETUS: Of course.
SOCRATES: Then my perception is true to me, being inseparable from my own being; and, as Protagoras says, to myself I am judge of what is and what is not to me.
THEAETETUS: I suppose so.
SOCRATES: How then, if I never err, and if my mind never trips in the conception of being or becoming, can I fail of knowing that which I perceive?
THEAETETUS: You cannot.
SOCRATES: Then you were quite right in affirming that knowledge is only perception; and the meaning turns out to be the same, whether with Homer and Heracleitus, and all that company, you say that all is motion and flux, or with the great sage Protagoras, that man is the measure of all things; or with Theaetetus, that, given these premises, perception is knowledge. Am I not right, Theaetetus, and is not this your new-born child, of which I have delivered you? What say you?
THEAETETUS: I cannot but agree, Socrates.
SOCRATES: Then this is the child, however he may turn out, which you and I have with difficulty brought into the world. And now that he is born, we must run round the hearth with him, and see whether he is worth rearing, or is only a wind-egg and a sham. Is he to be reared in any case, and not exposed? or will you bear to see him rejected, and not get into a passion if I take away your first-born?
THEODORUS: Theaetetus will not be angry, for he is very good-natured. But tell me, Socrates, in heaven's name, is this, after all, not the truth?
SOCRATES: You, Theodorus, are a lover of theories, and now you innocently fancy that I am a bag full of them, and can easily pull one out which will overthrow its predecessor. But you do not see that in reality none of these theories come from me; they all come from him who talks with me. I only know just enough to extract them from the wisdom of another, and to receive them in a spirit of fairness. And now I shall say nothing myself, but shall endeavour to elicit something from our young friend.
THEODORUS: Do as you say, Socrates; you are quite right.
SOCRATES: Shall I tell you, Theodorus, what amazes me in your acquaintance Protagoras?
THEODORUS: What is it?
SOCRATES: I am charmed with his doctrine, that what appears is to each one, but I wonder that he did not begin his book on Truth with a declaration that a pig or a dog-faced baboon, or some other yet stranger monster which has sensation, is the measure of all things; then he might have shown a magnificent contempt for our opinion of him by informing us at the outset that while we were reverencing him like a God for his wisdom he was no better than a tadpole, not to speak of his fellow-men – would not this have produced an overpowering effect? For if truth is only sensation, and no man can discern another's feelings better than he, or has any superior right to determine whether his opinion is true or false, but each, as we have several times repeated, is to himself the sole judge, and everything that he judges is true and right, why, my friend, should Protagoras be preferred to the place of wisdom and instruction, and deserve to be well paid, and we poor ignoramuses have to go to him, if each one is the measure of his own wisdom? Must he not be talking 'ad captandum' in all this? I say nothing of the ridiculous predicament in which my own midwifery and the whole art of dialectic is placed; for the attempt to supervise or refute the notions or opinions of others would be a tedious and enormous piece of folly, if to each man his own are right; and this must be the case if Protagoras' Truth is the real truth, and the philosopher is not merely amusing himself by giving oracles out of the shrine of his book.
THEODORUS: He was a friend of mine, Socrates, as you were saying, and therefore I cannot have him refuted by my lips, nor can I oppose you when I agree with you; please, then, to take Theaetetus again; he seemed to answer very nicely.
SOCRATES: If you were to go into a Lacedaemonian palestra, Theodorus, would you have a right to look on at the naked wrestlers, some of them making a poor figure, if you did not strip and give them an opportunity of judging of your own person?
THEODORUS: Why not, Socrates, if they would allow me, as I think you will, in consideration of my age and stiffness; let some more supple youth try a fall with you, and do not drag me into the gymnasium.
SOCRATES: Your will is my will, Theodorus, as the proverbial philosophers say, and therefore I will return to the sage Theaetetus: Tell me, Theaetetus, in reference to what I was saying, are you not lost in wonder, like myself, when you find that all of a sudden you are raised to the level of the wisest of men, or indeed of the gods? – for you would assume the measure of Protagoras to apply to the gods as well as men?
THEAETETUS: Certainly I should, and I confess to you that I am lost in wonder. At first hearing, I was quite satisfied with the doctrine, that whatever appears is to each one, but now the face of things has changed.
SOCRATES: Why, my dear boy, you are young, and therefore your ear is quickly caught and your mind influenced by popular arguments. Protagoras, or some one speaking on his behalf, will doubtless say in reply, – Good people, young and old, you meet and harangue, and bring in the gods, whose existence or non-existence I banish from writing and speech, or you talk about the reason of man being degraded to the level of the brutes, which is a telling argument with the multitude, but not one word of proof or demonstration do you offer. All is probability with you, and yet surely you and Theodorus had better reflect whether you are disposed to admit of probability and figures of speech in matters of such importance. He or any other mathematician who argued from probabilities and likelihoods in geometry, would not be worth an ace.
THEAETETUS: But neither you nor we, Socrates, would be satisfied with such arguments.
SOCRATES: Then you and Theodorus mean to say that we must look at the matter in some other way?
THEAETETUS: Yes, in quite another way.
SOCRATES: And the way will be to ask whether perception is or is not the same as knowledge; for this was the real point of our argument, and with a view to this we raised (did we not?) those many strange questions.
THEAETETUS: Certainly.
SOCRATES: Shall we say that we know every thing which we see and hear? for example, shall we say that not having learned, we do not hear the language of foreigners when they speak to us? or shall we say that we not only hear, but know what they are saying? Or again, if we see letters which we do not understand, shall we say that we do not see them? or shall we aver that, seeing them, we must know them?
THEAETETUS: We shall say, Socrates, that we know what we actually see and hear of them – that is to say, we see and know the figure and colour of the letters, and we hear and know the elevation or depression of the sound of them; but we do not perceive by sight and hearing, or know, that which grammarians and interpreters teach about them.
SOCRATES: Capital, Theaetetus; and about this there shall be no dispute, because I want you to grow; but there is another difficulty coming, which you will also have to repulse.
THEAETETUS: What is it?
SOCRATES: Some one will say, Can a man who has ever known anything, and still has and preserves a memory of that which he knows, not know that which he remembers at the time when he remembers? I have, I fear, a tedious way of putting a simple question, which is only, whether a man who has learned, and remembers, can fail to know?