No trace of slavery ought to mix with the studies of the freeborn man. No study, pursued under compulsion, remains rooted in the memory.
PlatoIf a man says that it is right to give every one his due, and therefore thinks within his own mind that injury is due from a just man to his enemies but kindness to his friends, he was not wise who said so, for he spoke not the truth, for in no case has it appeared to be just to injure any one.
Plato