The Republic by Plato Part 3 Page 82

wise judge whom we are seeking is not this man, but the other; for vice cannot know virtue too, but a virtuous nature, educated by time, will acquire a knowledge both of virtue and vice: the virtuous, and not the vicious, man has wisdom — in my opinion.

And in mine also.

This is the sort of medicine, and this is the sort of law, which you will sanction in your state. They will minister to better natures, giving health both of soul and of body; but those who are diseased in their bodies they will leave to die, and the corrupt and incurable souls they will put an end to themselves.

That is clearly the best thing both for the patients and for the State.

And thus our youth, having been educated only in that simple