Tell me, then, I said, what you mean to affirm about wisdom.

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?