"Perhaps there will be babblers who, although completely ignorant of mathematics, nevertheless dare to pass judgment on these things, and because of some passage in Holy Scripture, want to distort my b…"

"When, therefore, I had long considered the uncertainty of the traditional mathematical doctrines concerning the order of the spheres of the universe, I began to be annoyed that no more accurate explan…"

"The difficulty of the task, and the novelty of the opinion, almost deterred me from publishing the work."

"For the motions of the planets are so much more orderly and harmonious if they are referred to the sun as the center."

"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."