"The custom of believing what others believe, and of doing what others do, is the most powerful obstacle to the discovery of truth."

"I consider that I possess no senses; I imagine that body, figure, extension, motion and place are but fictions of my mind."

"The greatest good is that which is most useful."

"I resolved to seek no other knowledge than that which I might find within myself, or in the great book of the world."

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