Mathematics is the language with which God has written the universe.

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

All truths are easy to understand once they are discovered; the point is to discover them.

You cannot teach a man anything, you can only help him to find it for himself.

Wine is "light held together by moisture."

My dear Kepler, what would you say of the learned here, who, replete with the pertinacity of the asp, have steadfastly refused to cast a glance through the telescope? What shall we make of this? Shall we laugh, or shall we cry?

I never met a man so unknowledgeable, I could not learn something from him.

And yet it moves. About the earth, the comment he is rumored to have made after his recantation before the Inquisition.

See now the power of truth; the same experiment which at first glance seemed to show one thing, when more carefully examined, assures us of the contrary.

Alas! Your dear friend and servant Galileo has been for the last month hopelessly blind; so that this heaven, this earth, this universe, which I by my marvelous discoveries and clear demonstrations had enlarged a hundred thousand times beyond the belief of the wise men of bygone ages, henceforward for me is shrunk into such a small space as is filled by my own bodily sensations.

I have for many years been a partisan of the Copernican view because it reveals to me the causes of many natural phenomena that are entirely incomprehensible in the light of the generally accepted hypothesis. To refute the latter I have collected many proofs, but I do not publish them, because I am deterred by the fate of our teacher Copernicus who, although he had won immortal fame with a few, was ridiculed and condemned by countless people (for very great is the number of the stupid) Letter to Kepler

Surely, God could have caused birds to fly with their bones made of solid gold, with their veins full of quicksilver, with their flesh heavier than lead, and with their wings exceedingly small. He did not, and that ought to show something. It is only in order to shield your ignorance that you put the Lord at every turn to the refuge of a miracle.

The great book of nature is written in mathematical symbols.

If you could see the earth illuminated when you were in a place as dark as night, it would look to you more splendid than the moon.

Mathematics is the key and door to the sciences.

Philosophy is written in this grand book— I mean the universe— which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.

I have been in my bed for five weeks, oppressed with weakness and other infirmities from which my age, seventy four years, permits me not to hope release. Added to this ( proh dolor! ) the sight of my right eye – that eye whose labors (dare I say it) have had such glorious results - is for ever lost. That of the left, which was and is imperfect, is rendered null by continual weeping. July 4, 1637

I was obliged to retract, like a good Catholic, this opinion of mine; and as a punishment my dialogue was prohibited; and after five months being dismissed from Rome (at the time that the city of Florence was infected with plague), the habitation which with generous pity was assigned to me, was that of the dearest friend I had in Siena, Monsignor the Archbishop Piccolomini, whose most agreeable conversation I enjoyed with such quite and satisfaction of mind, that having there resumed my studies, I discovered and demonstrated a great number on the mechanical conclusions on the resistance of solids…after about five months, the pestilence having ceased, the confinement of that house was changed by His Holiness for the freedom of the country so agreeable to me, whence I returned to the villa of Bellosguardo, and afterwards to Arcetri, where I still breathe salubrious air near my dear native-country Florence. Letters to Fr. Vincenzo Renieri

I am certainly interested in a tribunal in which, for having used my reason, I was deemed little less than a heretic. Who knows but men will reduce me from the profession of a philosopher to that of historian of the Inquisition! But they behave to me in order that I may become the ignoramous and the fool of Italy... Letters to Fr. Vincenzo Renieri

After the publication of my dialogues, I was summoned to Rome by the Congregation of the holy Office, where, being arrived on the 10th of February 1633, I was subjected to the infinite clemency of that tribunal, and of the Sovereign Pontiff, Urban the Eighth; who, notwithstanding, thought me deserving of his esteem. Letters to Fr. Vincenzo Renieri

Detractors of corruptibility deserve being turned into statues.