Where have they gone, the brilliant, the insightful ones, the proud? Book VIII

The answer comes from the realization that genes for behavior, as well as for malaria resistance and teeth, are subject to natural selection. Why Is Sex Fun?: The Evolution of Human Sexuality

[One of the company... said: ...is not this the direct contrary of what we admitted before—that out of the greater came the less and out of the less the greater, and that opposites are simply generated from opposites; whereas now this seems to be utterly denied.] ...then we were speaking of opposites in the concrete, and now of the essential opposite which, as is affirmed, neither in us nor in nature can ever be at variance with itself... these essetial opposites will never, as we maintain, admit of generation into or out of one another. The Trials Of Socrates

By a tranquil mind I mean nothing else than a mind well ordered. Book IV