The purpose of punishment is to improve those who do the punishing--that is the final recourse of those who support punishment.
One is punished best for one's virtues.
Without cruelty there is no festival: thus the longest and most ancient part of human history teaches and in punishment there is so much that is festive!
Speaking generally, punishment hardens and numbs, it produces concentration, it sharpens the consciousness of alienation, it strengthens the power of resistance.
All in all, punishment hardens and renders people more insensible; it concentrates; it increases the feeling of estrangement; it strengthens the power of resistance.