To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge.
In the midst of all dwells the Sun. For who could set this luminary in another or better place in this most glorious temple, than whence he can at one and the same time brighten the whole.
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.
Of all things visible, the highest is the heaven of the fixed stars.
The earth together with its surrounding waters must in fact have such a shape as its shadow reveals, for it eclipses the moon with the arc of a perfect circle.
In so many and such important ways, then, do the planets bear witness to the earth’s mobility.
For it is the duty of an astronomer to compose the history of the celestial motions through careful and expert study.
Therefore, when I considered this carefully, the contempt which I had to fear because of the novelty and apparent absurdity of my view, nearly induced me to abandon utterly the work I had begun.
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.
Although all the good arts serve to draw man’s mind away from vices and lead it toward better things, this function can be more fully performed by this art, which also provides extraordinary intellectual pleasure.