"If you would be a real seeker after truth, you must at least once in your life doubt, as far as possible, all things."

"I know not if I was then a man dreaming I was a butterfly, or if I am now a butterfly dreaming I am a man."

"I can establish as a general rule that all things which I perceive very clearly and distinctly are true."

"Illusory joy is often worth more than genuine sorrow."

"Nothing comes out of nothing."

-Rene Descartes