Hypotheses non fingo. I frame no hypotheses.

To arrive at the simplest truth requires years of contemplation.

I understood. I have understood. I do understand.

What Descartes did was a good step. You have added much several ways, and especially in taking the colours of thin plates into philosophical consideration. If I have seen a little further it is by standing on the shoulders of Giants.

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.

Nature does nothing in vain when less will serve; for Nature is pleased with simplicity and affects not the pomp of superfluous causes.

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