"Therefore, if any motions are attributed to the earth, they must produce in the celestial phenomena an appearance exactly the reverse of that which is observed."

"For I have found that the motions of the planets are more regular and orderly if the Earth is assumed to move."

"And so, having obtained the opportunity, I now propose to explain the motions of the heavenly bodies, and the order of the universe, with greater certainty than has hitherto been possible."

"For I am convinced that the world is a single, unified system, and that all its parts are interrelated."

"Indeed, I am aware that a philosopher's thoughts are far removed from the judgment of the multitude, for his aim is to seek the truth in all things, to the extent permitted to human reason by God."