Once we know our weaknesses they cease to do us any harm.

One is rarely an impulsive innovator after the age of sixty, but one can still be a very fine orderly and inventive thinker. One rarely procreates children at that age, but one is all the more skilled at educating those who have already been procreated, and education is procreation of another kind.

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

When a book and a head collide and a hollow sound is heard, must it always have come from the book?

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.

Everyone should study at least enough philosophy and belles-lettres to make his sexual experience more delectable.

We cannot remember too often that when we observe nature, and especially the ordering of nature, it is always ourselves alone we are observing.