When, however, you have an enemy, then do not requite him good for evil: for that would shame him. Instead, prove that he did some good for you. And rather be angry than put to shame! And when you are cursed, I do not like it that you want to bless. Rather curse a little also! And if you are done a great injustice, then quickly add five small ones. Hideous to behold is he who is obsessed with an injustice.
At last a vision has been vouchsafed to us of our life as a whole. We see the bad with the good.... With this vision we approach new affairs. Our duty is to cleanse, to reconsider, to restore, to correct the evil without impairing the good, to purify and humanize every process of our common life, without weakening or sentimentalizing it.
You do not settle whether an argument is justified by merely showing that it is of some use. The distinction is not between useful and useless experiments but between barbarous and civilized behaviour. Vivisection is a social evil because if it advances human knowledge, it does so at the expense of human character.
Happiness of any given life is to be measured, not by its joys and pleasures, but by the extent to which it has been free from suffering-from positive evil.