"It is necessary to know the causes of things, and not only their effects, if we wish to have perfect knowledge."

"The true method of philosophy is by experiment and experience."

"The present generation is so corrupt that it despises the truth, and loves falsehood."

"The true knowledge is hidden from the common people, and is only revealed to a few."

"The study of optics is of the greatest utility, for it teaches us to understand the nature of light, and of all things that are visible."