Letters 88.28

Now philosophy asks no favours from any other source; it builds everything on its own soil; but the science of numbers is, so to speak, a structure built on another man’s land—it builds on alien soil. It accepts first principles, and by their favour arrives at further conclusions. If it could march unassisted to the truth, if it were able to understand the nature of the universe, I should say that it would offer much assistance to our minds; for the mind grows by contact with things heavenly, and draws into itself something from on high. There is but one thing that brings the soul to perfection—the unalterable knowledge of good and evil. But there is no other art which investigates good and evil.

I should like to pass in review the several virtues.

Seneca, Letters to Lucilius 88.28, translated by Richard Mott Gummere