The Republic by Plato Part 3 Page 84

What then is the real object of them?

I believe, I said, that the teachers of both have in view chiefly the improvement of the soul.

How can that be? he asked.

Did you never observe, I said, the effect on the mind itself of exclusive devotion to gymnastic, or the opposite effect of an exclusive devotion to music?

In what way shown? he said.

The one producing a temper of hardness and ferocity, the other of softness and effeminacy, I replied.

Yes, he said, I am quite aware that the mere athlete becomes too much of a savage, and that the mere musician is melted and softened beyond what is good for him.