There is nothing more ancient than the truth.

Thus each truth discovered was a rule available in the discovery of subsequent ones.

Sensations are nothing but confused modes of thinking.

The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once.

The first precept was never to accept a thing as true until I knew it as such without a single doubt.

The greatest minds are capable of the greatest vices as well as of the greatest virtues.

Common sense is the most widely shared commodity in the world, for every man is convinced that he is well supplied with it.