Shakespeare's genius was a better thing than Shakespeare's Othello. Ordinarily, the cause is not permanently exhausted by the effort of causation; more remains behind than has been put into the effect. A man is more proud of what he can do than of what he has done. There would be small satisfaction in viewing a work of your mind, or of your hands, if you felt that your hand had lost its cunning, and your mind was now effete.

Of God and His Creatures: 1.23