Philosophy is such an impertinently litigious lady that a man had as good be engaged in lawsuits as have to do with her.

From what has been said it is also evident, that the Whiteness of the Sun's Light is compounded all the Colours wherewith the several sorts of Rays whereof that Light consists, when by their several Refrangibilities they are separated from one another, do tinge Paper or any other white Body whereon they fall. For those Colours ... are unchangeable, and whenever all those Rays with those their Colours are mix'd again, they reproduce the same white Light as before.

This principle of nature being very remote from the conceptions of Philosophers, I forbore to describe it in that book, least I should be accounted an extravagant freak and so prejudice my Readers against all those things which were the main designe of the book.

Therefore to the same natural effects we must, as far as possible, assign the same causes.

Because of Diamond, I have had to begin much of the work afresh. I will not, however, rid myself of her, nor even punish her. She knew not what she was doing, and that which she did was for my protection and for love of my person. Her place remains at my side or against my feet when I lie abed.

The wonderful arrangement and harmony of the cosmos would only originate in the plan of an almighty omniscient being. This is and remains my greatest comprehension.

Pictures, propagated by motion along the fibers of the optic nerves in the brain, are the cause of vision.