"The first precept was never to accept anything for true which I did not clearly know to be such."

"I am a thinking thing, a substance whose whole essence or nature consists in thinking, and there is no need of any place, nor does it depend on any material thing."

"The preservation of health has always been the principal end of my studies."

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

"The nature of the mind is entirely distinct from that of the body."