Rene Descartes

"The two operations of our understanding, intuition and deduction, on which alone we have said we must rely in the acquisition of knowledge."

"I am indeed amazed when I consider how weak my mind is and how prone to error."

"I am accustomed to sleep and in my dreams to imagine the same things that lunatics imagine when awake."

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

"The reading of all good books is like a conversation with the finest minds of past centuries."

"I hope that posterity will judge me kindly, not only as to the things which I have explained, but also to those which I have intentionally omitted so as to leave to others the pleasure of discovery."