"It is a mark of a truly great mind to be able to make a great discovery with few means."

"I confess that I have never been able to find out what is the 'substantial form' of a human body, or how it differs from the form of a statue."

"The first precept was never to accept a thing as true until I knew it as such without a single doubt."

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

"The perception of the understanding is sometimes obscure and confused, while that of the will is always clear and distinct."