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

If another Messiah was born he could hardly do so much good as the printing-press.

People often become scholars for the same reason they become soldiers: simply because they are unfit for any other station. Their right hand has to earn them a livelihood; one might say they lie down like bears in winter and seek sustenance from their paws.

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.

With God thoughts are colors, with us they are pigments-even the most abstract one may be accompanied by physical pain.

A handful of soldiers is always better than a mouthful of arguments.

The most heated defenders of a science, who cannot endure the slightest sneer at it, are commonly those who have not made very much progress in it and are secretly aware of this defect.