The feeling of health can only be gained by sickness.

Nothing can contribute more to peace of soul than the lack of any opinion whatever.

It is a sure evidence of a good book if it pleases us more and more as we grow older.

One has to do something new in order to see something new.

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

We say that someone occupies an official position, whereas it is the official position that occupies him.

Perhaps in time the so-called Dark Ages will be thought of as including our own.