Nothing makes one old so quickly as the ever-present thought that one is growing older.

A sure sign of a good book is that you like it more the older you get.

A good method of discovery is to imagine certain members of a system removed and then see how what is left would behave: for example, where would we be if iron were absent from the world: this is an old example.

Barbaric accuracy - whimpering humility.

He was then in his fifty-fourth year, when even in the case of poets reason and passion begin to discuss a peace treaty and usually conclude it not very long afterwards.

Man is a masterpiece of creation if for no other reason than that, all the weight of evidence for determinism notwithstanding, he believes he has free will.

Above all things expand the frontiers of science: without this the rest counts for nothing.