The Republic by Plato Part 1 Page 50

What do you mean?

I mean what I may illustrate negatively by the example of the body. Suppose you were to ask me whether the body is self-sufficing or has wants, I should reply: Certainly the body has wants; for the body may be ill and require to be cured, and has therefore interests to which the art of medicine ministers; and this is the origin and intention of medicine, as you will acknowledge.

Am I not right?

Quite right, he replied.

But is the art of medicine or any other art faulty or deficient in any quality in the same way that the eye may be deficient in sight or the ear fail of hearing, and therefore requires another art to provide for the interests of seeing and hearing — has art in itself, I say, any