Galileo Galilei Quotes on Knowledge
Galileo's Dialogue Concerning the Two Chief World Systems (1632) and Two New Sciences (1638) gave the early modern scientific revolution its principal philosophical statements. The Dialogue's defense of Copernican heliocentrism against the Ptolemaic-Aristotelian geocentrism it eventually replaced earned Galileo's condemnation by the Roman Inquisition; the more enduring philosophical achievement was the program of mathematical natural philosophy: the book of nature is written in the language of mathematics, and the proper investigation of natural phenomena proceeds through quantitative measurement, controlled experiment, and the abstraction of mathematical laws of motion from the irrelevant qualitative variation of particular cases. The framework displaced the Aristotelian natural philosophy of qualitative form and final cause that had organized Western natural inquiry since the high Middle Ages.
Quotes
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Attributed to Galileo Galilei:
“Philosophy is written in this grand book, the universe, which stands continually open to our gaze. But the book cannot be understood unless one first learns to comprehend the language and read the letters in which it is composed. It is written in the language of mathematics.”
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“I do not feel obliged to believe that the same God who has endowed us with sense, reason, and intellect has intended us to forgo their use.”
Letter to the Grand Duchess Christina -
Attributed to Galileo Galilei:
“All truths are easy to understand once they are discovered; the point is to discover them.”
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“In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.”
sì perché l'autorità dell'opinione di mille nelle scienze non val per una scintilla di ragione di un solo, sì perché le presenti osservazioni spogliano d'autorità i decreti de' passati scrittori, i quali se vedute l'avessero, avrebbono diversamente determinato. -
Attributed to Galileo Galilei:
“Measure what is measurable, and make measurable what is not so.”
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“Quòd tertio loca à nobis fuit obſeruatum, eſt ipſiuſmet LACTEI Circuli eſſentia, ſeu materies, quam Perſpicilli beneficio adeò ad ſenſum licet intueri, vt & altercationes omnes, quæ per tot ſæcula Philoſophos excrucia runt ab oculata certitudine dirimantur, nosque à verboſis dſputationibus liberemur.”
What was observed by us in the third place is the nature or matter of the Milky Way itself, which, with the aid of the spyglass, may be observed so well that all the disputes that for so many generations have vexed philosophers are destroyed by visible certainty , and we are liberated from wordy arguments . Original text as reproduced in Edward Tufte, Beautiful Evidence (Cheshire, Connecticut: Gra -
“Revealing great, unusual, and remarkable spectacles, opening these to the consideration of every man, and especially of philosophers and astronomers ; as observed by Galileo Galilei, Gentleman of Florence , Professor of Mathematics in the University of Padua , with the aid of a spyglass lately invented by him, in the surface of the Moon , in innumerable fixed stars , in nebulae, and above all in four planets swiftly revolving about Jupiter at differing distances and periods, and known to no one before the author recently perceived them and decided they should be named the Medicean Stars”
Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957) -
“Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)”
Revealing great, unusual, and remarkable spectacles, opening these to the consideration of every man, and especially of philosophers and astronomers ; as observed by Galileo Galilei, Gentleman of Florence , Professor of Mathematics in the University of Padua , with the aid of a spyglass lately invented by him, in the surface of the Moon , in innumerable fixed stars , in nebulae, and above all in f -
“Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)”
About ten months ago a report reached my ears that a certain Fleming had constructed a spyglass by means of which visible objects, though very distant from the eye of the observer, were distinctly seen as if nearby. Of the truly remarkable effect several experiences were related, to which some persons gave credence while others denied them. A few days later a report was confirmed to me in a letter -
“Surely it is a great thing to increase the numerous host of fixed stars previously visible to the unaided vision , adding countless more which have never before been seen, exposing these plainly to the eye in numbers ten times exceeding the old and familiar stars.”
Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957) -
“Translation by Stillman Drake in Discoveries and Opinions of Galileo (1957)”
Surely it is a great thing to increase the numerous host of fixed stars previously visible to the unaided vision , adding countless more which have never before been seen, exposing these plainly to the eye in numbers ten times exceeding the old and familiar stars. -
“Copernicus never discusses matters of religion or faith , nor does he use argument that depend in any way upon the authority of sacred writings which he might have interpreted erroneously. ... He did not ignore the Bible, but he knew very well that if his doctrine were proved, then it could not contradict the Scriptures when they were rightly understood.”
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