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

[1.] And first I suppose that there is diffused through all places an aethereal substance capable of contraction & dilatation, strongly elastick, & in a word, much like air in all respects, but far more subtile. 2. I suppose this aether pervades all gross bodies, but yet so as to stand rarer in their pores then in free spaces, & so much ye rarer as their pores are less ... 3. I suppose ye rarer aether within bodies & ye denser without them, not to be terminated in a mathematical superficies, but to grow gradually into one another.

The best way to understanding is a few good examples.

No great discovery was ever made without a bold guess.

If the ancient churches, in debating and deciding the greatest mysteries of religion, knew nothing of these two texts, I understand not why we should be so fond of them now the debate is over.

The great ocean of truth lay all undiscovered before me.

'Tis the temper of the hot and superstitious part of mankind in matters of religion ever to be fond of mysteries, and for that reason to like best what they understand least.