"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 chief cause of human error is the confused nature of our perceptions."

"It is proper to a philosopher to doubt everything, at least once."

"I consider that I possess no senses; I imagine that body, figure, extension, motion and place are but fictions of my mind."

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