In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.

Their vain presumption of knowing all can take beginning solely from their never having known anything; for if one has but once experienced the perfect knowledge of one thing, and truly tasted what it is to know, he shall perceive that of infinite other conclusions he understands not so much as one.

To command their professors of astronomy to refute their own observations is to command them not to see what they do see and not to understand what they do understand.

See now the power of truth.

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

Showing a greater fondness for their own opinions than for truth, they sought to deny and disprove the new things which, if they had cared to look for themselves, their own senses would have demonstrated to them.

Two truths cannot contradict one another.