"My entire life has been directed toward the acquisition of knowledge."

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

"Except our own thoughts, there is nothing absolutely in our power."

"The long chains of simple and easy reasonings by means of which geometers are accustomed to reach the conclusions of their most difficult demonstrations, had led me to imagine that all things, the kno…"

"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."