Meno (89)

Then may we assert this as a universal rule, that in man all other things depend upon the soul, while the things of the soul herself depend upon wisdom,

Certainly.

Hence we conclude that virtue is either wholly or partly wisdom?

It seems to me that your statement, Socrates, is excellent.

Then if this is so, good men cannot be good by nature.

I think not.

No, for then, I presume, we should have had this result: if good men were so by nature, we surely should have had men able to discern who of the young were good by nature, and on their pointing them out we should have taken them over and kept them safe in the citadel, having set our mark on them far rather than on our gold treasure, in order that none might have tampered with them, and that when they came to be of age, they might be useful to their country.

Yes, most likely, Socrates.

So since it is not by nature that the good become good,

We must now conclude, I think, that it is; and plainly, Socrates, on our hypothesis that virtue is knowledge, it must be taught.

Yes, I daresay; but what if we were not right in agreeing to that?

Well, it seemed to be a correct statement a moment ago.

Yes, but not only a moment ago must it seem correct, but now also and hereafter, if it is to be at all sound.

Why, what reason have you to make a difficulty about it, and feel a doubt as to virtue being knowledge?

I will tell you, Meno. I do not withdraw as incorrect the statement that it is taught, if it is knowledge; but as to its being knowledge, consider if you think I have grounds for misgiving. For tell me now: if anything at all, not merely virtue, is teachable, must there not be teachers and learners of it?

I think so.

Then also conversely, if a thing had neither teachers nor learners, we should be right in surmising that it could not be taught?

That is so: but do you think there are no teachers of virtue?