(T)he increase of known truths stimulates the investigation, establishment, and growth of the arts.
The sun, with all he planets revolving around it, and depending on it, can still ripen a bunch of grapes as though it had nothing else in the universe to do.
Passion is the genesis of genius.
Mathematics is the key and door to the sciences.
To be humane, we must ever be ready to pronounce that wise, ingenious and modest statement 'I do not know'.
It is a beautiful and delightful sight to behold the body of the Moon.
In the long run my observations have convinced me that some men, reasoning preposterously, first establish some conclusion in their minds which, either because of its being their own or because of their having received it from some person who has their entire confidence, impresses them so deeply that one finds it impossible ever to get it out of their heads.
In the sciences, the authority of thousands of opinions is not worth as much as one tiny spark of reason in an individual man.
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.
In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.
The greatest wisdom is to get to know oneself.
You cannot teach a man anything, you can only help him find it within himself.
The doctrine that the earth is neither the center of the universe nor immovable, but moves even with a daily rotation, is absurd, and both philosophically and theologically false, and at the least an error of faith.
The book of nature is written in the language of mathematics.
The vain presumption of understanding everything can have no other basis than never having understood anything. For anyone who had ever experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is accomplished, would recognize that of the infinity of other truths he understands nothing.
E pur si muove. "Albeit It does move". (That's what Galileo purportedly muttered after torturers forced him to recant his theory that the earth orbits the sun.)
You may force me to say what you wish; you may revile me for saying what I do. But it moves.
We see only the simple motion of descent, since that other circular one common to the Earth, the tower, and ourselves remains imperceptible. There remains perceptible to us only that of the stone, which is not shared by us; and, because of this, sense shows it as by a straight line, always parallel to the tower, which is built upright and perpendicular upon the terrestrial surface.
God is known by nature in his works, and by doctrine in his revealed word.
The sun, with all those planets revolving around it and dependent on it, can still ripen a bunch of grapes as if it had nothing else in the universe to do.
All truths are easy to understand once they are discovered; the point is to discover them.
I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forego their use.
I've loved the stars too fondly to be fearful of the night.
Mathematics is the language with which God has written the universe.
Two truths cannot contradict one another.
Knowing thyself, that is the greatest wisdom.
I have never met a man so ignorant that I couldn't learn something from him.
We cannot teach people anything; we can only help them discover it within themselves.
I abjure with a sincere heart and unfeigned faith, I curse and detest the said errors and heresies, and generally all and every error and sect contrary to the Holy Catholic Church.
With regard to matters requiring thought: the less people know and understand about them, the more positively they attempt to argue concerning them.
The theologians also should not be irritated. For if they find that this opinion is false, then they would be free to condemn it; and if they discover that it is true, they ought to thank those who have opened the way to finding the true sense of the Scriptures and who have prevented them from falling into the grave scandal of condemning a true proposition.
Who would dare assert that we know all there is to be known?
Measure what is measurable, and make measurable what is not so.
Holy Scripture could never lie or err...its decrees are of absolute and inviolable truth.
If I were again beginning my studies, I would follow the advice of Plato and start with mathematics.
Infinities and indivisibles transcend our finite understanding, the former on account of their magnitude, the latter because of their smallness; Imagine what they are when combined.
I think that in the discussion of natural problems we ought to begin not with the Scriptures, but with experiments, and demonstrations.
Science proceeds more by what it has learned to ignore than what it takes into account.
There are those who reason well, but they are greatly outnumbered by those who reason badly.
But what exceeds all wonders, I have discovered four new planets and observed their proper and particular motions, different among themselves and from the motions of all the other stars; and these new planets move about another very large star [Jupiter] like Venus and Mercury, and perchance the other known planets, move about the Sun. As soon as this tract, which I shall send to all the philosophers and mathematicians as an announcement, is finished, I shall send a copy to the Most Serene Grand Duke, together with an excellent spyglass, so that he can verify all these truths.