Every light has its shadow, and every shadow hath a succeeding morning.

I can easily conceive, most Holy Father, that as soon as some people learn that in this book which I have written concerning the revolutions of the heavenly bodies, I ascribe certain motions to the Earth, they will cry out at once that I and my theory should be rejected.

In so many and such important ways, then, do the planets bear witness to the earth's mobility.

Mathematics is written for mathematicians.

I am aware that a philosopher's ideas are not subject to the judgment of ordinary persons, because it is his endeavour to seek the truth in all things, to the extent permitted to human reason by God.

So, influenced by these advisors and this hope, I have at length allowed my friends to publish the work, as they had long besought me to do.

More stars in the north are seen not to set, while in the south certain stars are no longer seen to rise.