I inherited a vile melancholy from my father, which has made me mad all my life, at least not sober.

I had rather see the portrait of a dog that I know, than all the allegorical paintings they can show me in the world.

No member of a society has a right to teach any doctrine contrary to what the society holds to be true.

None of the projects or designs which exercise the mind of man are equally subject to obstructions and disappointments with the pursuit of fame.

Timidity is a disease of the mind, obstinate and fatal; for a man once persuaded that any impediment is insuperable has given it, with respect to himself, that strength and weight which it had not before.

Everything that enlarges the sphere of human powers, that shows man he can do what he thought he could not do, is valuable.

Tomorrow is an old deceiver, and his cheat never grows stale.