If an opinion contrary to your own makes you angry, that is a sign that you are subsciously aware of having no good reason for thinking as you do. [...] The most savage controversies are those about matters as to which there is no good evidence either way. Persecution is used in theology, not in arithmetic, because in arithmetic there is knowledge, but in theology there is only opinion. So whenever you find yourself getting angry about a difference of opinion, be on your guard; you will probably find, on examination, that your belief is going beyond what the evidence warrants.

...the nonexistence of God makes more difference to some of us than to others. To me, it means that there is no absolute morality, that moralities are sets of social conventions devised by humans to satisfy their needs.

Few people can be happy unless they hate some other person, nation, or creed.

Every great idea starts out as a blasphemy.

Not to be absolutely certain is, I think, one of the essential things in rationality.

In view of the fact that in any future world war nuclear weapons will certainly be employed, and that such weapons threaten the continued existence of mankind, we urge the governments of the world to realize, and to acknowledge publicly, that their purpose cannot be furthered by a world war, and we urge them, consequently, to find peaceful means for the settlement of all matters of dispute between them.

There is in Aristotle an almost complete absence of what may be called benevolence or philanthropy. The sufferings of mankind . . . there is no evidence that they cause him unhappiness except when the sufferers happen to be his friends.