I am not a pessimist: to perceive evil where it exists is, in my opinion, a form of optimism.
- Roberto Rosselini
He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss, the abyss gazes also into you.
- Friedrich Nietzsche
We ought always to deal justly, not only with those who are just to us, but likewise to those who endeavor to injure us; and this, for fear lest by rendering them evil for evil, we should fall into the same vice.