"I found myself constrained to believe that there are certain principles which the human mind spontaneously accepts as true."

"The existence of God is clearly demonstrated by the very idea of God."

"The senses deceive from time to time, and it is prudent never to trust wholly those who have deceived us even once."

"Doubt is the origin of wisdom."

"The mind is a substance whose whole essence or nature is to think, and which needs no place, nor depends on any material thing, in order to exist."