The reading of all good books is indeed like a conversation with the noblest men of past centuries who were the authors of them, nay a carefully studied conversation, in which they reveal to us none but the best of their thoughts.

Let whoever can do so deceive me, he will never bring it about that I am nothing, so long as I continue to think I am something.

Science is practical philosophy.

Your joy is your sorrow unmasked. And the self-same well from which your laughter rises was often-times filled with your tears.

[About Pierre de Fermat] It cannot be denied that he has had many exceptional ideas, and that he is a highly intelligent man. For my part, however, I have always been taught to take a broad overview of things, in order to be able to deduce from them general rules, which might be applicable elsewhere.

Bad books engender bad habits, but bad habits engender good books.

An optimist may see a light where there is none, but why must the pessimist always run to blow it out?