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.
Life is a flame that is always burning itself out; but it catches fire again every time a child is born. Life is greater than death, and hope than despair.
To withhold deserved praise lest it should make its object conceited is as dishonest as to withhold payment of a just debt lest your creditor should spend the money badly.
All classes in proportion to their lack of travel and familiarity with foreign literature are bellicose, prejudiced against foreigners, fond of fighting as a cruel sport - in short, dog-like in their notions of foreign policy.
The fact that we can become accustomed to anything, however disgusting at first, makes it necessary to examine carefully everything we have become accustomed to.
If a group of beings from another planet were to land on Earth - beings who considered themselves as superior to you as you feel yourself to be to other animals - would you concede them the rights over you that you assume over other animals?