In first place we must observe that the universe is spherical. This is either because that figure is the most perfect, as not being articulated, but whole and complete in itself; or because it is the most capacious and therefore best suited for that which is to contain and preserve all things.

In the midst of all dwells the sun.

Astronomy is written for astronomers

Of all things visible, the highest is the heaven of the fixed stars.

For I am not so enamoured of my own opinions that I disregard what others may think of them.

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.

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