"We are to admit no more causes of natural things than such as are both true and sufficient to explain their appearances."

"If I have seen further than others, it is by standing upon the shoulders of giants."

"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."

"The particles of light are exceedingly small, and move with exceeding swiftness."

"Every body continues in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed upon it."