I have remarked very clearly that I am often of one opinion when I am lying down and of another when I am standing up.

Never undertake anything unless you have the heart to ask Heaven's blessing on your undertaking.

Most men of education are more superstitious than they admit - nay, than they think.

The great trick of regarding small departures from the truth as the truth itself - on which is founded the entire integral calculus - is also the basis of our witty speculations, where the whole thing would often collapse if we considered the departures with philosophical rigour.

We have no words for speaking of wisdom to the stupid. He who understands the wise is wise already.

There is no greater impediment to progress in the sciences than the desire to see it take place too quickly.

To be content with life or to live merrily, rather all that is required is that we bestow on all things only a fleeting, superficial glance; the more thoughtful we become the more earnest we grow.