Mathematics Is Written For Mathematicians.

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.

The Scorn Which I Had Reason To Fear On Account Of The Novelty And Unconventionality Of My Opinion Almost Induced Me To Abandon Completely The Work Which I Had Undertaken. . . . Astronomy Is Written For Astronomers. To Them My Work Too Will Seem, Unless I Am Mistaken, To Make Some Contribution.

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.

Not Only The Phenomena Of The Others Followed From This, But Also It So Bound Together Both The Order And Magnitude Of All The Planets And The Spheres And The Heaven Itself, That In No Single Part Could One Thing Be Altered Without Confusion Among The Other Parts And In All The Universe.

At Rest, However, In The Middle Of Everything Is The Sun.