SOCRATES: The reason why I am thus precise is, because I want to know whether, when we perceive black and white through the eyes, and again, other qualities through other organs, we do not perceive them with one and the same part of ourselves, and, if you were asked, you might refer all such perceptions to the body. Perhaps, however, I had better allow you to answer for yourself and not interfere. Tell me, then, are not the organs through which you perceive warm and hard and light and sweet, organs of the body? THEAETETUS: Of the body, certainly. SOCRATES: And you would admit that what you perceive through one faculty you cannot perceive through another; the objects of hearing, for example, cannot be perceived through sight, or the objects of sight through hearing? THEAETETUS: Of course not. SOCRATES: If you have any thought about both of them, this common perception cannot come to you, either through the one or the other organ? THEAETETUS: It cannot. SOCRATES: How about sounds and colours: in the first place you would admit that they both exist? THEAETETUS: Yes. SOCRATES: And that either of them is different from the other, and the same with itself? THEAETETUS: Certainly. SOCRATES: And that both are two and each of them one? THEAETETUS: Yes. SOCRATES: You can further observe whether they are like or unlike one another? THEAETETUS: I dare say. SOCRATES: But through what do you perceive all this about them? for neither through hearing nor yet through seeing can you apprehend that which they have in common. Let me give you an illustration of the point at issue:--If there were any meaning in asking whether sounds and colours are saline or not, you would be able to tell me what faculty would consider the question. It would not be sight or hearing, but some other. THEAETETUS: Certainly; the faculty of taste. SOCRATES: Very good; and now tell me what is the power which discerns, not only in sensible objects, but in all things, universal notions, such as those which are called being and not-being, and those others about which we were just asking--what organs will you assign for the perception of these notions? THEAETETUS: You are thinking of being and not being, likeness and unlikeness, sameness and difference, and also of unity and other numbers which are applied to objects of sense; and you mean to ask, through what bodily organ the soul perceives odd and even numbers and other arithmetical conceptions. SOCRATES: You follow me excellently, Theaetetus; that is precisely what I am asking. THEAETETUS: Indeed, Socrates, I cannot answer; my only notion is, that these, unlike objects of sense, have no separate organ, but that the mind, by a power of her own, contemplates the universals in all things.