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?