Do not Bodies and Light act mutually upon one another; that is to say, Bodies upon Light in emitting, reflecting, refracting and inflecting it, and Light upon Bodies for heating them, and putting their parts into a vibrating motion wherein heat consists?

The best way to understanding is a few good examples.

. . . Newton was an unquestioning believer in an all-wise creator of the universe, and in his own inability - like the boy on the seashore - to fathom the entire ocean in all its depths. He therefore believed that there were not only many things in heaven beyond his philosophy, but plenty on earth as well, and he made it his business to understand for himself what the majority of intelligent men of his time accepted without dispute (to them it was as natural as common sense) - the traditional account of the creation.

Sir Isaac Newton was asked how he discovered the law of gravity. He replied, "By thinking about it all the time.

Nature is very consonant and conformable with herself.

Absolute, true and mathematical time, of itself, and from its own nature flows equably without relation to anything external.

I have not been able to discover the cause of those properties of gravity from phenomena, and I frame no hypotheses; for whatever is not deduced from the phenomena is to be called a hypothesis, and hypotheses, whether metaphysical or physical, whether of occult qualities or mechanical, have no place in experimental philosophy.