"To conquer myself rather than fortune, and to change my desires rather than the order of the world."

"I have never made any distinction between the sciences, but have always held that all are linked together, and that it is easier to learn them all at once than to learn one separately."

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

"I have never made any discoveries that were not based on the certainty of mathematics."

"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."