"Therefore, I propose that the earth moves, and that the fixed stars are immovable."

"First of all, the world is spherical. This is because the sphere is the most perfect figure of all, and it is the form of the world."

"For it is not necessary that hypotheses should be true, or even probable; it is enough if they provide a calculus which agrees with the observations."

"Nor do I doubt that learned and skillful mathematicians will agree with me if they are willing to give not superficial but profound attention to the arguments I adduce in this work."

"Nations are not ruined by one act of violence, but gradually and in an almost imperceptible manner by the depreciation of their circulating currency, through its excessive quantity."