One must judge men not by their opinions, but by what their opinions have made of them.

A writer who wishes to be read by posterity must not be averse to putting hints which might give rise to whole books, or ideas for learned discussions, in some corner of a chapter so that one should think he can afford to throw them away by the thousand.

With a pen in my hand I have successfully stormed bulwarks from which others armed with sword and excommunication have been repulsed.

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

With prophecies the commentator is often a more important man than the prophet.

So-called professional mathematicians have, in their reliance on the relative incapacity of the rest of mankind, acquired for themselves a reputation for profundity very similar to the reputation for sanctity possessed by theologians.

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