I mean to say that wisdom is the only science which is the science of itself as well as of the other sciences.

But the science of science, I said, will also be the science of the absence of science.

Very true, he said.

Then the wise or temperate man, and he only, will know himself, and be able to examine what he knows or does not know, and to see what others know and think that they know and do really know; and what they do not know, and fancy that they know, when they do not. No other person will be able to do this. And this is wisdom and temperance and self-knowledge--for a man to know what he knows, and what he does not know. That is your meaning?

Yes, he said.

Now then, I said, making an offering of the third or last argument to Zeus the Saviour, let us begin again, and ask, in the first place, whether it is or is not possible for a person to know that he knows and does not know what he knows and does not know; and in the second place, whether, if perfectly possible, such knowledge is of any use.

That is what we have to consider, he said.

And here, Critias, I said, I hope that you will find a way out of a difficulty into which I have got myself. Shall I tell you the nature of the difficulty?

By all means, he replied.

Does not what you have been saying, if true, amount to this: that there must be a single science which is wholly a science of itself and of other sciences, and that the same is also the science of the absence of science?

Yes.

But consider how monstrous this proposition is, my friend: in any parallel case, the impossibility will be transparent to you.

How is that? and in what cases do you mean?

In such cases as this: Suppose that there is a kind of vision which is not like ordinary vision, but a vision of itself and of other sorts of vision, and of the defect of them, which in seeing sees no colour, but only itself and other sorts of vision: Do you think that there is such a kind of vision?

Certainly not.

Or is there a kind of hearing which hears no sound at all, but only itself and other sorts of hearing, or the defects of them?

There is not.

Or take all the senses: can you imagine that there is any sense of itself and of other senses, but which is incapable of perceiving the objects of the senses?

I think not.

Could there be any desire which is not the desire of any pleasure, but of itself, and of all other desires?

Certainly not.

Or can you imagine a wish which wishes for no good, but only for itself and all other wishes?

I should answer, No.

Or would you say that there is a love which is not the love of beauty, but of itself and of other loves?

I should not.

Or did you ever know of a fear which fears itself or other fears, but has no object of fear?

I never did, he said.

Or of an opinion which is an opinion of itself and of other opinions, and which has no opinion on the subjects of opinion in general?

Certainly not.

But surely we are a.s.suming a science of this kind, which, having no subject-matter, is a science of itself and of the other sciences?

Yes, that is what is affirmed.

But how strange is this, if it be indeed true: we must not however as yet absolutely deny the possibility of such a science; let us rather consider the matter.

You are quite right.

Well then, this science of which we are speaking is a science of something, and is of a nature to be a science of something?

Yes.

Just as that which is greater is of a nature to be greater than something else? (Socrates is intending to show that science differs from the object of science, as any other relative differs from the object of relation. But where there is comparison--greater, less, heavier, lighter, and the like--a relation to self as well as to other things involves an absolute contradiction; and in other cases, as in the case of the senses, is hardly conceivable. The use of the genitive after the comparative in Greek, (Greek), creates an unavoidable obscurity in the translation.)

Yes.

Which is less, if the other is conceived to be greater?

To be sure.

And if we could find something which is at once greater than itself, and greater than other great things, but not greater than those things in comparison of which the others are greater, then that thing would have the property of being greater and also less than itself?

That, Socrates, he said, is the inevitable inference.

Or if there be a double which is double of itself and of other doubles, these will be halves; for the double is relative to the half?

That is true.

And that which is greater than itself will also be less, and that which is heavier will also be lighter, and that which is older will also be younger: and the same of other things; that which has a nature relative to self will retain also the nature of its object: I mean to say, for example, that hearing is, as we say, of sound or voice. Is that true?

Yes.

Then if hearing hears itself, it must hear a voice; for there is no other way of hearing.

Certainly.

And sight also, my excellent friend, if it sees itself must see a colour, for sight cannot see that which has no colour.

No.

Do you remark, Critias, that in several of the examples which have been recited the notion of a relation to self is altogether inadmissible, and in other cases hardly credible--inadmissible, for example, in the case of magnitudes, numbers, and the like?