[ Alleged remark after recanting his position that the earth moves around the sun, 1632 :] Eppur si muove .

Philosophy is written in this grand book, the universe, which stands continually open to our gaze. . . . It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures without which . . . one wanders about in a dark labyrinth.

Desiring to remove from the minds of Your Eminences, and of all faithful Christians, this vehement suspicion rightly conceived against me, with sincere heart and unpretended faith I abjure, curse, and detest the aforesaid errors and heresies . . . and I swear that in the future I will never again say or assert verbally or in writing, anything that might cause a similar suspicion toward me.

In questions of science, the writerity of a thousand is not worth the humble reasoning of a single individual.

I have never met a man so ignorant that I couldn't learn something from him.

Mathematics is the language with which God has written the universe.

I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.

Long experience has taught me this about the status of mankind with regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them, while on the other hand to know and understand a multitude of things renders men cautious in passing judgement upon anything new.

All truths are easy to understand once they are discovered; the point is to discover them.

The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.