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

"The light of natural reason is sufficient to distinguish the true from the false."

"I resolved to feign that all the perceptions I had ever received were no truer than the illusions of my dreams."

"If you would be a real seeker after truth, it is necessary that at least once in your life you doubt, as far as possible, all things."

"I found it possible to reject all my former beliefs, and to admit nothing as true that I had not clearly conceived."