"The light of natural reason shows us that there is a God."

"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, to the …"

"I have long ago observed that in order to study the truth, it is necessary once in the course of our life to demolish everything completely and start again from the foundations."

"The existence of God is a necessary consequence of my idea of God."

"The power of judging well and of distinguishing the true from the false, which is properly what is called good sense or reason, is by nature equal in all men."