I therefore concluded, and decided unhesitatingly, that there are three stars in the heavens moving about Jupiter, as Venus and Mercury about the Sun; which at length was established as clear as daylight by numerous other observations.

Some, merely to contradict what I had said, did not scruple to cast doubt upon things they had seen with their own eyes again and again.

In the sciences, the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.

It seems to me that it was well said by Madama Serenissima, and insisted on by your reverence, that the Holy Scripture cannot err, and that the decrees therein contained are absolutely true and inviolable. But I should have in your place added that, though Scripture cannot err, its expounders and interpreters are liable to err in many ways; and one error in particular would be most grave and most frequent, if we always stopped short at the literal signification of the words.

Who would dare assert that we know all there is to be known?

Vision, I say, is related to light itself. But of this sensation and the things pertaining to it, I pretend to understand but little; and since even a long time would not suffice to explain that trifle, or even to hint at an explanation, I pass over this in silence.

To understand the Universe, you must understand the language in which it's written, the language of Mathematics.