We are mad, not only individually, but nationally. We check manslaughter and isolated murders; but what of war and the much-vaunted crime of genocide? There are no limits to our greed, and neither to our cruelty. And as long as such crimes are committed by stealth and by individuals, they are less harmful and less portentous; but cruelties are practiced in accordance with acts of the senate or of a popular assembly, and the public is invited to do that which formerly was forbidden to the individual. So we come to this clearest manifestation of insanity: that deeds which rightfully would be punished with a sentence of death when committed by an ordinary man, are suddenly praised and celebrated when committed by a general wearing a uniform. By his nature man is a gentle creature, yet does he not revel in the blood of others without shame? … Against this overmastering and widespread madness, philosophy comes as a matter of great effort, only slowly assuming the strength gathered by the forces of barbarity.
—Lucius Annaeus Seneca, Ad Lucilium epistulae morales, epis xcv, sec 30-33 (CE 64) (S.H. transl.)