Deliberate virtue is never worth much: The virtue of feeling or habit is the thing.

Be wary of passing the judgment: obscure. To find something obscure poses no difficult, elephants and poodles find many things obscure.

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.

The man was such an intellectual he was of almost no use.

I have often noticed that when people come to understand a mathematical proposition in some other way than that of the ordinary demonstration, they promptly say, "Oh, I see. That's how it must be." This is a sign that they explain it to themselves from within their own system.

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

Be attentive, feel nothing in vain, measure and compare: this is the whole law of philosophy.