So far I have been speaking of theoretical science, which is an attempt to understand the world. Practical science, which is an attempt to change the world, has been important from the first, and has continually increased in importance, until it has almost ousted theoretical science from men's thoughts.

Perhaps the nuclear physicists have come so near to the ultimate secrets that He thinks it time to bring their activities to a stop. And what simpler method could He devise than to let them carry their ingenuity to the point where they exterminate the human race?

Fools and fanatics are always so certain of themselves.

More cranks take up unfashionable errors than unfashionable truths.

Fear is the parent of cruelty, and therefore it is no wonder if cruelty and religion have gone hand-in-hand. It is because fear is at the basis of those two things. In this world we can now begin a little to understand things, and a little to master them by the help of science, which has forced its way step by step against the Christian religion, against the churches, and against the opposition of all the old precepts.

I've always thought respectable people scoundrels, and I look anxiously at my face every morning for signs of my becoming a scoundrel.

The fact that an opinion has been widely held is no evidence whatever that it is not utterly absurd.