"I know that I exist, but I do not know what I am."

"It is not enough to have a good mind; the main thing is to use it well."

"I was very surprised to find that I had been mistaken more often than not in my life."

"I entirely abandoned the study of letters, resolving to seek no other science than that which could be found in myself, or at least in the great book of the world."

"I suppose therefore that all the things I see are false imaginations; I believe that nothing ever existed of all that my fallacious memory represents to me."