Just as courage imperils life, fear protects it.

One day the world will look upon research upon animals as it now looks upon research on human beings.

Art is never finished, only abandoned.

A deaf and dumb person who sees two men in conversation - may nevertheless understand from the attitudes and gestures of the speakers, how well their discussion is getting along.

The poet ranks far below the painter in the representation of visible things, and far below the musician in that of invisible things.

Obstacles cannot crush me. Every obstacle yields to stern resolve. He who is fixed to a star does not change his mind.

There is no higher or lower knowledge, but one only, flowing out of experimentation.