Everyone Should Read What Galileo Wrote
Why should everyone read what Galileo wrote? To see what he did that they probably have not done during their lives to the point of time they are reading what he wrote. Like, read what Aristotle had written nearly two millennia earlier? What Galileo wrote is only about four centuries ago.
And certainly we need to consider what has occurred during these four centuries which had not occurred during the previous two millennia to understand the possible profit of reading what Galileo wrote.
We need to read what Galileo wrote to see that he had the same problem that Aristotle had. What was this problem? Galileo wrote (as translated by Henry Crew and Alfonso de Salvio):
I must neglect no experiment or argument to establish it. But what was it?  The facts set forth by me up to this point and, in particular, the one which shows that difference of weight, even when very great, is without effect in changing the speed of falling bodies, so that as far as weight is concerned that all fall with equal speed: this idea is, I say, so new, and at first glance so remote from fact, that if we do no not have the means of making it just as clear as sunlight, it had better not be mentioned; but having once allowed it to pass my lips I must neglect no experiment or argument to establish it.
Hence, Galileo believed he could establish fact by argument just as Aristotle had successfully done for nearly two millennia while knowing he had absolutely refuted Aristotle’s argument by simple experiment (observation).
This is why ‘everyone should read what Galileo wrote’ so we, in the science established by Galileo, would stop making the same mistake made by Aristotle and then by Galileo. Which is believing that scientific fact can be established by argument.
When I first read Dialogues Concerning Two New Sciences as translated by Crew and de Salvio I was confused by the fact that Galileo did not once mention the name (person) Copernicus; who had died about 21 years before Galileo was born. This spring (2017) I discovered, by what I conclude was pure accident, an 1840 book by David Brewster which was titled The Martyrs of Science.
In it Brewster wrote:
“It is not easy to ascertain the exact time when Galileo became a convert to the doctrines of Copernicus … It has been ably shown, by the latest biographer of Galileo, [Life of Galileo, in Library of Useful Knowledge, p-9] that, in his dialogues on the Copernican system, our author gives the true account of his own conversion. “
This passage is so interesting, that we should read the entirety:Â
“I cannot omit this opportunity of relating to you what happened to myself at the time when this opinion (the Copernican system) began to be discussed. I was then a very young man, and had scarcely finished my course of philosophy, which other occupations obliged me to leave off, when there arrived in this country, from Rostoch, a foreigner, whose name, I believe, was Christian Vurstisius (Wurteisen), a follower of Copernicus. This person delivered, on this subject, two or three lectures in a certain academy, and to a crowded audience. Believing that several were attracted more by the novelty of the subject than by any other cause, and being firmly persuaded that this opinion was a piece of solemn folly, I was unwilling to be present. Upon interrogating, however, some of those who were there, I found that they all made it a subject of merriment, with the exception of one, who assured me that it was not a thing wholly ridiculous. As I considered this individual to be both prudent and circumspect, I repented that I had not attended the lectures; and, whenever I met any of the followers of Copernicus, I began to inquire if they had always been of the same opinion. I found that there was not one of them who did not declare that he had long maintained the very opposite opinions, and had not gone over to the new doctrines till he was driven by the force of argument. I next examined them one by one, to see if they were masters of the arguments on the opposite side; and such was the readiness of their answers, that I was satisfied they had not taken up this opinion from ignorance or vanity. On the other hand, whenever I interrogated the Peripatetics and the Ptolemeans—and, out of curiosity, I have interrogated not a few—respecting their perusal of Copernicus’s work, I perceived that there were few who had seen the book, and not one who understood it. Nor have I omitted to inquire among the followers of the Peripatetic doctrines, if any of them had ever stood on the opposite side; and the result was, that there was not one. Considering, then, that nobody followed the Copernican doctrine, who had not previously held to the contrary opinion, and who was not well acquainted with the arguments of Aristotle and Ptolemy; while, on the other hand, nobody followed Ptolemy and Aristotle, who had before adhered to Copernicus, and had gone over from him into the camp of Aristotle;–weighing, I say, these things, I began to believe that, if any one who rejects an opinion which he has imbibed with his milk, and which has been embraced by an infinite number, shall take up an opinion held only by a few, condemned by all the schools, and really regarded as a great paradox, it cannot be doubted that he must have been induced, not to say driven, to embrace it by the most cogent arguments. On this account I have become very curious to penetrate to the very bottom of the subject. “[Systema Cosmicum, Dial. ii. p. 121]
The two other Martyrs of Science about whom Brewster wrote were Tycho Brahe and Johannes Kepler. Contemporaries of Galileo whose efforts of observation (Brahe) and Kepler’s analysis of Brahe’s observations, which produced three scientific laws (still not refuted by observation) concerning the motion of planets as they revolved about the sun, were rejected by Galileo because he, the founder of modern physical science, evidently still accepted that scientific fact (observations) could be refuted by argument.
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