"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."

"I feign no hypotheses."

"Gravity must be caused by some agent acting constantly according to certain laws; but whether this agent be material or immaterial, I have left to the consideration of my readers."

"For if the experiments which I relate be accurate, the science of colours will be a new one; for although colours have been observed from antiquity, yet the cause of their productions has remained unk…"

"The light which comes from the sun, and from all fire, consists of all the primary colours mixed together."