Theaetetus (186)

THEAET. Well, I do think so.

SOC. To which class, then, do you assign being; for this, more than anything else, belongs to all things?

THEAET. I assign them to the class of notions which the soul grasps by itself directly.

SOC. And also likeness and unlikeness and identity and difference?

THEAET. Yes.

SOC. And how about beautiful and ugly, and good and bad?

THEAET. I think that these also are among the things the essence of which the soul most certainly views in their relations to one another, reflecting within itself upon the past and present in relation to the future.

SOC. Stop there. Does it not perceive the hardness of the hard through touch, and likewise the softness of the soft?

THEAET. Yes.

SOC. But their essential nature and the fact that they exist, and their opposition to one another, and, in turn, the essential nature of this opposition, the soul itself tries to determine for us by reverting to them and comparing them with one another.

THEAET. Certainly.

SOC. Is it not true, then, that all sensations which reach the soul through the body, can be perceived by human beings, and also by animals, from the moment of birth; whereas reflections about these, with reference to their being and usefulness, are acquired, if at all, with difficulty and slowly, through many troubles, in other words, through education?

THEAET. Assuredly.

SOC. Is it, then, possible for one to attain truth who cannot even get as far as being?

THEAET. No.

SOC. And will a man ever have knowledge of anything the truth of which he fails to attain?

THEAET. How can he, Socrates?

SOC. Then knowledge is not in the sensations, but in the process of reasoning about them; for it is possible, apparently, to apprehend being and truth by reasoning, but not by sensation.

THEAET. So it seems.

SOC. Then will you call the two by the same name, when there are so great differences between them?

THEAET. No, that would certainly not be right.

SOC. What name will you give, then, to the one which includes seeing, hearing, smelling, being cold, and being hot?

THEAET. Perceiving. What other name can I give it?

SOC. Collectively you call it, then, perception?

THEAET. Of course.

SOC. By which, we say, we are quite unable to apprehend truth, since we cannot apprehend being, either.

THEAET. No; certainly not.

SOC. Nor knowledge either, then.

THEAET. No.

SOC. Then, Theaetetus, perception and knowledge could never be the same.

THEAET. Evidently not, Socrates; and indeed now at last it has been made perfectly clear that knowledge is something different from perception.