It often takes more courage to change one's opinion than to stick to it.

One of the greatest creations of the human mind is the art of reviewing books without having read them.

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

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.

Pain warns us not to exert our limbs to the point of breaking them. How much knowledge would we not need to recognize this by the exercise of mere reason.

What most clearly characterizes true freedom and its true employment is its misemployment.

There is a great difference between believing in something and believing in it again.