Without my attempts in natural science, I should never have learned to know mankind such as it is. In nothing else can we so closely approach pure contemplation and thought, so closely observe the errors of the senses and of the understanding, the weak and strong points of character.

Some books seem to have been written, not to teach us anything, but to let us know that the author has known something.

Stupidity is without anxiety.

Battle not with monsters, for then you become one.

Let's plunge ourselves into the roar of time, the whirl of accident; may pain and pleasure, success and failure, shift as they will -- it's only action that can make a man.

Beware of wishing for anything in youth, because you will get it in middle age.

If in the infinite you want to stride, Just walk in the finite to every side.