"Divide each difficulty into as many parts as is feasible and necessary to resolve it."

"I shall proceed by setting aside all that in which I can suppose there to be the slightest doubt, just as if I had discovered that it was wholly false."

"Perfect numbers like perfect men are very rare."

"It is precisely because I am in the habit of using my senses to think of things that I find it difficult to think of anything else."

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