See now the power of truth.

Where the senses fail us, reason must step in.

To excite in us tastes, odors, and sounds I believe that nothing is required in external bodies except shapes, numbers, and slow or rapid movements. ... if ears, tongues, and noses were removed, shapes and numbers and motions would remain, but not odors or tastes or sounds.

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

Names and attributes must be accommodated to the essence of things, and not the essence to the names, since things come first and names afterwards.

Science proceeds more by what it has learned to ignore than what it takes into account.

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.