Throughout the long period of religious doubt, I had been rendered very unhappy by the gradual loss of belief, but when the process was completed, I found to my surprise that I was quite glad to be done with the whole subject.

It's easy to fall in love. The hard part is finding someone to catch you.

Man can be scientifically manipulated.

I am firm; YOU are obstinate; HE is a pig-headed fool.

The human race may well become extinct before the end of the century.

Memory demands an image.

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.