All who are not lunatics are agreed about certain things. That it is better to be alive than dead, better to be adequately fed than starved, better to be free than a slave. Many people desire those things only for themselves and their friends; they are quite content that their enemies should suffer. These people can only be refuted by science: Humankind has become so much one family that we cannot ensure our own prosperity except by ensuring that of everyone else. If you wish to be happy yourself, you must resign yourself to seeing others also happy.