The earth, in fair and grateful exchange, pays back to the moon an illumination similar to that which it receives from her throughout nearly all the darkest gloom of the night.

One can understand nature only when one has learned the language and the signs in which it speaks to us; but this language is mathematics and these signs are methematical figures.

There are those who reason well, but they are greatly outnumbered by those who reason badly.

The Grand Duke [of Tuscany] ...after observing the Medicaean plants several times with me ... has now invited me to attach myself to him with the annual salary of one thousand florins, and with the title of Philosopher and Principal Mathematicial to His Highness; without the duties of office to perform, but with the most complete leisure; so that I can complete my Treatises.

I think that in the discussion of natural problems we ought to begin not with the Scriptures, but with experiments, and demonstrations.

I am inclined to think that the authority of Holy Scripture is intended to convince men of those truths which are necessary for their salvation, which, being far above man's understanding, can not be made credible by any learning, or any other means than revelation by the Holy Spirit.

Mathematics is the key and door to the sciences.