SOC. Let us stick close to the statement we made a moment ago, and assume that nothing exists by itself as invariably one: then it will be apparent that black or white or any other color whatsoever is the result of the impact of the eye upon the appropriate motion, and therefore that which we call color

 
will be in each instance neither that which impinges nor that which is impinged upon, but something between, which has occurred, peculiar to each individual. Or would you maintain that each color appears to a dog, or any other animal you please, just as it does to you? THEAET. No, by Zeus, I wouldn’t. SOC. Well, does anything whatsoever appear the same to any other man as to you? Are you sure of this? Or are you not much more convinced that nothing appears the same even to you, because you yourself are never exactly the same? THEAET. Yes, I am much more convinced of the last. SOC. Then, if that with which I compare myself in size, or which I touch,
 
were really large or white or hot, it would never have become different by coming in contact with something different, without itself changing; and if, on the other hand, that which did the comparing or the touching were really large or white or hot, it would not have become different when something different approached it or was affected in some way by it, without being affected in some way itself. For nowadays, my friend, we find ourselves rather easily forced to make extraordinary and absurd statements, as Protagoras and everyone who undertakes to agree with him would say. THEAET. What do you mean? What statements? SOC. Take a little example and you will know all I have in mind. Given six dice, for instance, if you compare four with them, we say that they are more than the four, half as many again, but if you compare twelve with them, we say they are less, half as many; and any other statement would be inadmissible; or would you admit any other? THEAET. Not I. SOC. Well then, if Protagoras, or anyone else, ask you, Theaetetus, can anything become greater or more in any other way than by being increased? what reply will you make? THEAET. If I am to say what I think, Socrates, with reference to
 
the present question, I should say no, but if I consider the earlier question, I should say yes, for fear of contradicting myself. SOC. Good, by Hera! Excellent, my friend! But apparently, if you answer yes it will be in the Euripidean spirit; for our tongue will be unconvinced, but not our mind. Eur. Hipp. 612 ἡ γλῶσσ’ ὀμώμοχ’, ἡ δὲ φρὴν ἀνώμοτος , my tongue has sworn, but my mind is unsworn. THEAET. True. SOC. Well, if you and I were clever and wise and had found out everything about the mind, we should henceforth spend the rest of our time testing each other out of the fulness of our wisdom,
 
rushing together like sophists in a sophistical combat, battering each other’s arguments with counter arguments. But, as it is, since we are ordinary people, we shall wish in the first place to look into the real essence of our thoughts and see whether they harmonize with one another or not at all. THEAET. Certainly that is what I should like.