"The greatest good is the knowledge of truth, and the greatest evil is error."

"To be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it."

"I can easily conceive that there is nothing in the world, that there is no heaven, no earth, no minds, no bodies; is it not then likewise true that I do not exist?"

"My purpose is not to teach a method which everyone ought to follow to guide his reason, but only to show how I have tried to guide mine."

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