The universe may have a purpose, but nothing we know suggests that, if so, this purpose has any similarity to ours.

To the young I should offer two maxims: Don't accept superficial solutions of difficult problems. It is better to do a little good than much harm. I should not offer anything more specific; every young person should decide on his or her own credo.

I did not know I loved you until I heard myself telling so, for one instance I thought, "Good God, what have I said?" and then I knew it was true.

In astronomy, the law of gravitation is plainly better worth knowing than the position of a particular planet on a particular night, or even on every night throughout a year. There are in the law a splendour and simplicity and sense of mastery which illuminate a mass of otherwise uninteresting details. But in history the matter is far otherwise. Historical facts, many of them, have an intrinsic value, a profound interest on their own account, which makes them worthy of study, quite apart from any possibility of linking them together by means of causal laws.

It has become a commonplace that aggressiveness also often has its roots in fear. I am inclined to think that this theory has been pushed too far. [...] The type of aggressiveness that is the outcome of timidity is not, I think, that which inspires great leaders; the great leaders, I should say, have an exceptional self-confidence which is not only on the surface, but penetrates deep into the subconscious.

Fools and fanatics are always so certain of themselves.

Whatever we know without inference is mental.