The main Business of Natural Philosophy is to argue from Phænomena without feigning Hypotheses, and to deduce Causes from Effects till we come to the very first Cause, which certainly is not mechanical; and not only to unfold the Mechanism of the World, but chiefly to resolve these, and to such like Questions.

By such deductions the law of gravitation is rendered probable, that every particle attracts every other particle with a force which varies inversely as the square of the distance. The law thus suggested is assumed to be universally true.

No old Men (excepting Dr. Wallis) love Mathematicks.

Oh Diamond! Diamond! thou little knowest the mischief done! [Apocryphal]

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.

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

God is able to create particles of matter of several sizes and figures and perhaps of different densities and forces, and thereby to vary the laws of nature, and make worlds of several sorts in several parts of the Universe.