I can calculate the motion of heavenly bodies but not the madness of people. - Isaac Newton

The Ellipse is the most simple of the Conic Sections, most known, and nearest of Kin to a Circle, and easiest describ'd by the Hand in plano. Though many prefer the Parabola before it, for the Simplicity of the Æquation by which it is express'd. But by this Reason the Parabola ought to be preferr'd before the Circle it self, which it never is. Therefore the reasoning from the Simplicity of the Æquation will not hold. The modern Geometers are too fond of the Speculation of Æquations.

What is there in places empty of matter? and Whence is it that the sun and planets gravitate toward one another without dense matter between them? Whence is it that Nature doth nothing in vain? and Whence arises all that order and beauty which we see in the world? To what end are comets, and whence is it that Planets move all one and the same way in Oorbs concentrick, while comets move all manner of ways in Orbs very excentrick; and what hinders the fix'd Stars from falling upon one another?

Gravity explains the motions of the planets, but it cannot explain who sets the planets in motion.