Demetrius

For instance, the art of healing has incidentally studied the nature of disease, and the art of harmony the nature of discord, in order to produce their opposites; and the most consummate arts of all, namely, temperance, justice, and wisdom, since their function is to distinguish, not only what is good and just and expedient, but also what is bad and unjust and disgraceful, have no praises for a guilelessness which plumes itself on its inexperience of evil, nay, they consider it to be foolishness, and ignorance of what ought especially to be known by men who would live aright.

Accordingly, the ancient Spartans would put compulsion upon their helots at the festivals to drink much unmixed wine, and would then bring them into the public messes, in order to show their young men what it was to be drunk. And though I do not think that the perverting of some to secure the setting right of others is very humane, or a good civil policy,

still, when men have led reckless lives, and have become conspicuous, in the exercise of power or in great undertakings, for badness, perhaps it will not be much amiss for me to introduce a pair or two of them into my biographies, though not that I may merely divert and amuse my readers by giving variety to my writing.