When the adversaries of Erasmus had got the Trinity into his edition, they threw by their manuscript as an old almanac out of date.

A man may imagine things that are false, but he can only understand things that are true, for if the things be false, the apprehension of them is not understanding.

This most beautiful system of the sun, planets and comets could only proceed from the counsel and dominion of an intelligent and powerful Being. And if the fixed stars are the centres of other like systems, these, being formed by the like wise counsel, must be all subject to the dominion of One; especially since the light of the fixed stars is of the same nature with the light of the sun.

[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.

Centripetal force is the force by which bodies are drawn from all sides, are impelled, or in any way tend, toward some point as to a center.

I do not feign hypotheses.

My Design in this Book is not to explain the Properties of Light by Hypotheses, but to propose and prove them by Reason and Experiments: In order to which, I shall premise the following Definitions and Axioms.