By Paul Newall (2005)
As we shall see, the Assayer was not just a polemic, in spite of the declarations to that effect on the part of several writers on Galileo (cf. de Santillana, 1958; Geymonat, op cit). Commenting on the fact that the myriad areas touched upon and arguments used have confused some scholars, Biagioli became befuddled himself when he referred to so-called Feyerabendian opportunism as an explanation for Galileo's employment of "ad hoc hypotheses, internal contradictions, and unjustified attacks" (1993: 268). Preferring to see Galileo's response within the context of patronage and as an attempt to reinforce his belief that he, and not Brah , was the pre-eminent post-Copernican astronomer, Biagioli failed to consider the possibility that Galileo was employing a reductio, a far more accurate "Feyerabendian" reading of the problematic existence of inconsistencies (cf. Farrell, 2003: 12-17 and further). This is part of a general trend among Galileo scholars that praises him for his genius as a rhetorician at one moment and ignores the most potent tool in any polemic the next in seeking to explain why the text does not form a cogent whole. Drake, at least, had noticed this (1999, 1: 30).
Before moving on to consider the other aspects of the Assayer, it is illuminating to compare Galileo's situation at this time—and hence—with that of John Wilkins in England. A vociferous defender of Copernicanism, he faced little opposition and was able to publish his Discovery of a world in the moon (1638) and Discourse concerning a new planet (1640) with ease. Although his career as an academic was put at risk by his alleged sympathies with the Royalist cause, his "survival as warden of Wadham [the Oxford College], his move to the mastership of Trinity College Cambridge in 1659, his becoming bishop of Chester in 1668, and his appointment as Lent preacher to the king suggest that there was nothing particularly hazardous in being England's most conspicuous Copernican" (Brooke, 1991: 107-108). To explain the Galileo affair simplistically as an instance of the supposed conflict between science and religion, then, is to invite the question as to why the reaction to Copernicanism differed between countries that were all religious (cf. Russell, 1991: 83-88).
Galileo's work and the criticism it faced were not just rhetoric, politics and patronage. In this second section we shall look at Galileo's science and its development, along with the philosophical aspects to the affair. In particular, we shall look again at the objections raised against his ideas.
Galileo and Science
Many pages have been authored on the subject of Galileo's scientific personality, a significant proportion of them concerned with "de-mythologising" Galileo and the view within the history of science that science proceeded (and proceeds) according to leaps of genius by greats like Galileo, Newton or Einstein. Some historians, however, have gone so far as to attribute to Galileo the character of a Copernican zealot who went far beyond reasonable scientific behaviour in seeking to convince others to accept conclusions for which there were insufficient grounds (for example, Koestler, 1959; Feyerabend, 1993; Shea and Artigas, 2003). This is the second myth we began with.
Johannes Kepler, Galileo’s correspondent and fellow astronomer
As we have noted above, Galileo regularly declined to publish his ideas when he felt they needed more work, whether his theories on motion or Copernicanism. He had preferred the second since the late 1590s but, lacking the telescopic observations that would show the Ptolemaic system to be false, he did not publicly support it until 1610. During his student days Galileo had rejected Copernicanism, setting out his reasons for so doing (Wallace, 1977: 71-74). Later, in a letter of 1597 to Kepler, he had written that
... I have already for many years come to accept the Copernican opinion and with this hypothesis have been able to explain many natural phenomena, which under the current hypotheses remain unexplainable. (X, 68—emphasis added)
Until his telescopic observations of the phases of Venus in late 1610, Galileo had no conclusive proof of the falsity of the Ptolemaic system, although he had come to believe the reality of the Copernican system. This is quite in accordance with a gradual development in both his thought and arguments (a full account of which was given by Drake (1999, 1: 351-363)) and the general principle he would later famously state in the following terms:
There is not a single effect in Nature, not even the least that exists, such that the most ingenious theorists can ever arrive at a complete understanding of it. This vain presumption of understanding everything can have no other basis than never understanding anything. For anyone who had experienced just once the perfect understanding of one single thing, and had truly tasted how knowledge is attained, would recognise that of the infinity of other truths he understands nothing. (Drake, 1953: 101)
In spite of passages like this and the principles enunciated in the Letter to Christina, some Galileo scholars have insisted that he was a convinced Copernican who was determined to battle dishonestly for a doctrine he knew to be unproven and for which he had no proof. When we understand these issues from the perspective of his wish to bring about the separation of science and religion, however, there are no such problematic excerpts to explain away as deliberately disingenuous or still more rhetoric: the telescope had sounded the death-knell for both the Ptolemaic and Tychonic systems and, even if this did not imply the truth of the Copernican alternative, it at least showed that the wedding of astronomical fact to Scriptural exegesis could not be maintained.
Much has been made of Galileo's writing in Italian, rather than the Latin then employed by most philosophers, theologians and the like. According to Feyerabend (1993), this was a rhetorical strategy on the part of Galileo, helping him to bypass the theologians and scholastics and appeal directly to the public; but it is hard to see how common opinion could have aided a zealous Copernican, even one of Galileo's stature, in swaying the decisions of the authoritarian Church. A far simpler explanation was given by Galileo himself in a letter of 1612:
What inspires me to do this [i.e. use Italian—or, more accurately, the Tuscan dialect] is my seeing how students in the universities, sent indiscriminately to become doctors, philosophers, etc., apply themselves in many cases to such professions when unsuited to them, while others who would be apt are occupied with family cares or with other pursuits remote from literature. Though well provided with horse sense, as Ruzzante would say, such men, being unable to read things written in Latin, become convinced that these wretched pamphlets containing the latest discoveries of logic and philosophy must remain forever over their heads. Now, I want them to see that just as Nature has given them, as well as philosophers, eyes to see her works, so she has also given them brains capable of grasping and understanding them. (Drake, 2001: 13-14)
This gives us an insight into Galileo's mentality: opposed to the idea that knowledge was exclusively the province of experts, he held that the book of Nature was open to all who would look rather than rely on the authority of Aristotle. Indeed, Galileo insisted that if Aristotle were somehow to return, he would be the first to oppose the doctrines justified in his name. In a very famous passage in the Assayer in which he was critical of this tendency, he laid out its failings:
In Sarsi I seem to discern the firm belief that in philosophizing one must support oneself upon the opinion of some celebrated author, as if our minds ought to remain completely sterile and barren unless wedded to the reasoning of some other person. Possibly he thinks that philosophy is a book of fiction by some writer, like the Iliad or Orlando Furioso, productions in which the least important thing is whether what is written is there is true. Well, Sarsi, that is not how matters stand. 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, 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 wanders about in a dark labyrinth. (VI, 232)
Many scholars have read this as indicative of Platonism in Galileo (Dijksterhuis makes this mistake, 1969: 337), but Drake explained (1999, 1: 53-54) that such a narrow reading misses the tripartite distinction Galileo was making between the universe, our attempts to understand it, and mathematics as a tool to aid us in so doing. This is very different from supposing mathematics to be the ultimate reality. Indeed, that Galileo did not even intend that philosophy had to be written in mathematical terms is immediate from the masterful way in which he used everyday metaphors, analogies and examples to explain his ideas. As an indicative instance, we may consider another excerpt from the Assayer that was beloved of Urban VIII. It concerns the story of a man who becomes fascinated by music and determines to seek out all possible sources of sound until he finds a cicada and becomes confused:
For having captured in his hands a cicada, he failed to diminish its strident noise either by closing its mouth or stopping its wings, yet he could not see it move the scales, which covered its body, or any other part. At last he lifted up the armour of its chest and there he saw some thin ligaments beneath, and thinking that the sound might come from their vibration, he decided to break them in order to silence it. But nothing happened until his needle drove too deep, and transfixing the creature he took away its life with its voice, so that he was still unable to determine whether the song had originated in those ligaments. This experience reduced him to diffidence, so that when asked how sounds were created he used to answer candidly that, although he knew some of the ways, he was certain many more existed that were unknown and unimaginable. (VI, 281)
Urban VIII was so pleased with the Assayer that he had it read to him while he ate (XIII, 141). This passage in particular embodied his own conviction that, since God could have created the universe in an infinity of ways, it was better to delight in that small part of it we may come to know than suppose useful hypotheses to be the whole truth on an issue.
Aside from attaching importance to mathematics as an instrumental language, Galileo also made a distinction between primary and secondary qualities (although he was not the first to do so) that would be taken up by Locke years later and which hinted at the mechanistic philosophy that would prove so important in the development of science (cf. Dijksterhuis, op cit: 333-359). When, in 1626, Grassi finally replied to the Assayer with his Ratio ponderum Librae et Simbellae, he took exception to the former, and specifically a passage in which Galileo had suggested that natural philosophy should be the study of "figures, numbers and local motion" (Fantoli, 1996: 293), not mere "names":
To excite in us tastes, odours and sounds I believe that nothing is required in external bodies except shapes, numbers, and slow or rapid movements. I think that if ears, tongues and noses were removed, shapes and numbers and motions would remain, but not odours or tastes or sounds. The latter, I believe, are nothing more than names when separated from living beings. (VII, 350)
This idea, still current in philosophy today and according to which eyes, light and wavelengths exist but "redness", say, does not, was seized upon by Grassi because he claimed that it had implications for the Catholic Eucharist, wherein bread is literally transformed into the body of Christ while maintaining its secondary qualities like taste and colour. If what was preserved as part of this miracle was nothing but "names", then nothing was preserved in reality and there is no miracle. Galileo was sufficiently worried by this accusation to ask Castelli to look into it (XIII, 389) and one Galileo scholar takes it as the basis of his interpretation of Galileo's subsequent trial (Redondi, 1987).
With Maffeo Barberini having ascended to the Papacy, Galileo again journeyed to Rome to pay his respects and to attempt to divine the attitude of the new Pope to his ideas and goals (XIII, 135). He arrived on the 23rd of April, 1624, and was granted no less than six audiences. He also met with Cardinals Antonio and Francesco Barberini, the brother and nephew of Urban VIII respectively (XIII, 175). On his departure in June, the Pontiff presented Galileo with a painting, a gold and a silver medal and several Agnus Dei. He was no closer to attaining his aim, however, and conceded that his discussions with Urban VIII had taught him that a prudent approach would be best (XIII, 179).
It is interesting to note the attitude that the Pope displayed toward the Copernican issue, considering more fully the instrumentalist thinking alluded to above. In an undated record of a conversation between Galileo and Urban VIII, the latter's Papal theologian, Agostino Oregio, explained that, having allowed all the arguments that Galileo had brought to bear on the question, the Pope
... asked him at the end whether God could not have the power and wisdom to dispose and move in another way the orbs and the stars and all that is seen in the sky and all that is said of the motions, order, location, distance and disposition of the stars... Because if God knew how and had the power to dispose all of this in another way than that which has been thought—in such wise as to save all that has been said—we cannot limit the divine power and wisdom to this way. (quoted by Fantoli, op cit, 322)
In response, said Oregio, "that most learned man [Galileo] remained silent." According to Urban VIII, then, astronomy must remain an instrumental science: if more than one system can save the appearances, or if there is no reason why other, currently unknown systems may not do likewise, we should view them as calculating devices or tools of prediction and not speak of their truth. This conception of theory evaluation will become important later.
Tommaso Campanella, a Dominican and one of Galileo’s supporters
Nevertheless, Galileo returned to Florence feeling that he could broach the issue of Copernicanism so long as he did so only in a hypothetical way. He decided to pursue a gradual course of action and devoted himself firstly to a paper that had been published back in 1616 by Francesco Ingoli, now secretary of the Congregation of the Propagation of the Faith. This pamphlet had disputed the Copernican system but, owing to the timing of events, Galileo had not felt that he could offer any rejoinder at that time. Kepler had already tackled Ingoli in 1618 and received a reply in turn. Galileo had been told by Tommaso Campanella (a Dominican who was imprisoned in Naples by the Inquisition for many years, largely for his political opinions, before his release by Urban VIII in 1629) in 1616 that he would author a criticism of Ingoli on his behalf (XII, 287), which Galileo declined—hardly the behaviour of a Copernican zealot but very much in keeping with a more accurate conception of Galileo as cautious and considered.
In his Letter to Ingoli, Galileo disavowed any theological argument and instead focused purely on the scientific areas of Ingoli's Disputio. Showing that the Copernican system was more in accordance with observation and reason, he explained that as a good Catholic he did not deny Copernicanism out of ignorance but instead because of the "reverence we have toward the writings of our Fathers" (VI, 511); that is, that Catholics were well aware of the support for Copernicus but, having understood it, placed their faith higher in import than interpreting astronomical theories as true representations. In part, this was in response to the suggestion in Protestant countries that the Church had banned all discussion of Copernicanism. This was referred to by Cardinal Zollern, Bishop of Osnabruck, who had reported to the Pope that "all heretics accept [Copernicus'] opinion and hold it as most certain" (XIII, 182). Attempts to convert Protestants in the German states were thus failing, he said, because of the perception there of the decree of 1616. Urban VIII had replied, according to Zollern, by saying that
... the Holy Church had not condemned [Copernicanism] nor was she about to condemn it now as heretical, but only as temerarious, though it was not to be feared that there would ever be anyone to demonstrate it as necessarily true. (ibid)
Much later, in 1630, Urban VIII would state that the decree "was never our intention; and if he had been left to us, that decree [of 1616] would not have been made" (XIV, 88).
Galileo's Letter took a long time to be published because the Church was investigating a complaint to the Holy Office concerning the Assayer. His friend Guidicci explained that a "pious person had proposed to prohibit or correct" the work (XIII, 265). According to a document discovered by Redondi in the archives of the Holy Office, the grievance also spoke of the atomism allegedly found in the Assayer as heretical (cf. Redondi, 1987: 137-202 for a discussion of this document and its anonymous author, together with 203-226 for more on the dispute on the Eucharist). The author objected that "if this philosophy of qualities is admitted to be true, it seems to me there follows a great difficulty in regard to the existence of the qualities of bread and wine which in the Holy Sacrament are separated from their own substance..." (in Finocchiaro, 1989: 203). Galileo's friends in Rome were understandably concerned.
Meanwhile Galileo returned to an idea that he first had when he moved to Padua (see Fantoli, op cit: 68), probably because it was more noticeable there: the phenomenon of the tides and their use as a possible argument against the fixed Earth. He wrote about it in several letters to friends in 1624 and still more in 1625 (XIII, 209 and 236, for example). This was to be the Discourse on the ebb and flow of the sea, in which he would consider the "two chief world systems" and the arguments for and against them, along with his thoughts on the tides and what they implied for the motion of the Earth. Although originally intending to finish the book swiftly (XIII, 295 suggests as much), family issues and health problems held him back. More importantly, it seems, the sheer scope of what he was attempting to achieve forced him to delay the writing as he sought more data and had to reconsider the direction he was taking in the light of objections (cf. XIV, 60).
After much work, Scheiner's response to Galileo was published in 1630 as Rosa Ursina, originally De Maculis Solis (or On Sunspots), Book One of which was largely a polemic against Galileo that took issue with his claims of plagiarism and reasserted Scheiner's priority (and independence) in the discovery of sunspots. Galileo's supporters replied in kind, but the far greater remainder of Scheiner's work was in fact a detailed critique of the incorruptibility of the heavens and other Aristotelian assumptions, coupled with "the most valuable treatise on solar physics of that epoch" (Fantoli, op cit: 332). Warned by Ciampoli via Castelli not to offer any comment (XIV, 330), perhaps to avoid any further deterioration in relations with the Jesuits, Galileo remained silent and continued with his own writing.
Late in 1629, Galileo was finally nearing the end of his work on the tides, completing it in April of the next year and writing to his French correspondent Elia Diodati that
In this [the Dialogue], besides the material on the tides, there will be inserted many other problems and a most ample confirmation of the Copernican system by showing the nullity of all that had been brought by Tycho and others to the contrary. (XIV, 49)
It is easy to read this as indicative of Galileo's zealous certainty of the truth of Copernicanism, but confirmation is not proof. We shall have occasion to discuss this distinction again below, but another letter to Buonamici gave a clear enough picture:
... I believe I have found the true reason for [the ebb and flow of the sea], very far from those to which up to now that effect has been attributed. I estimate it to be true and so do all of those with whom I have conferred about it. (XIV, 54)
We see here that Galileo believed and estimated the Copernican system to explain the tides, but that is a very long way from holding it to be certain and dedicating his life (or the greater part of it) to convincing others that it was so with all the rhetoric he could muster. (Indeed, at the close of his life Galileo apparently came to doubt the argument from the tides (XVII, 215)).
The Publication of the Dialogue
It was agreed late in 1629 that the Dialogue would be published in Rome, so Galileo again prepared to travel there to aid with the arrangements. Ill health intervened as usual, however, and it was May, 1630 before he arrived. He lodged with Francesco Niccolini, the Tuscan Ambassador since 1621, and his wife Caterina Riccardi (who was related to Niccol Riccardi, the Domincan who had cleared the Assayer for publication and written so highly of it). Galileo was again received by the Pope, the positive result of their discussions (XIV,105) apparently leaving him feeling he was free to publish his work.
At the same time, Galileo's enemies were just as busy, attributing to him a horoscope that foretold the death of Urban VIII and his nephew. The Pontiff, who was deeply superstitious, imprisoned the actual author, Orazio Morandi (who subsequently died in prison) and let it be known that Galileo "had no better friend than [Cardinal Francesco Barberini] and the Pope himself, and that he knew who he was and he knew that he did not have these kinds of matters in his head" (XIV, 111). Nevertheless, Urban VIII was under increasing political pressure as a result of the Thirty Years War and the strength of Cardinal Richelieu within France, such that Riccardi knew the publication of the Dialogue would have to be a delicate process.
Having realised that the Dialogue would be read as sympathetic to Copernicanism, the first thing Riccardi did was to insist that a preface and conclusion should be added, emphasising the hypothetical nature of the study and hence showing "that the Holy Congregation in reproving Copernicus had acted in an entirely reasonable way" (XIX, 325). He then passed the manuscript to Raffaele Visconti, Master of the Sacred Palace and also a professor of mathematics, who approved it. Riccardi was still not happy, though, possibly because he learned that Urban VIII had stated his annoyance at Galileo's claim that the tides depended on the motion of the Earth (XIV, 113—we can refer back to the Pontiff's instrumentalism to understand why). Riccardi decided to review it himself and discussed it with the Pope, who insisted that the title show no reference to the ebb and flow of the sea but instead should speak of the "Chief World Systems", or something similar. Satisfied that the imprimatur would be granted, Galileo returned to Florence after yet another visit to Urban VIII.
It had been agreed that the Dialogue would, as usual, be printed by the Accademia dei Lincei, but on the 1st of August 1630 Prince Cesi died, leaving neither will nor successor at the Academy. Following this deeply saddening event for Galileo, Castelli suggested that he perhaps look to publish in Florence instead (XIV, 135). When Riccardi was asked if he would agree to this arrangement, he declared that he would need a copy first in order to correct it, after which Galileo could publish it wherever he liked (XIV, 150). The plague then raging throughout Italy prevented both travel and post, however, so Galileo requested to be able to amend the work in Florence while leaving only the preface and conclusion to be eventually forwarded to Riccardi in Rome for his consideration. After a diplomatic battle, in which Ambassador Niccolini's wife leant heavily on her relative, Riccardi agreed, with the caveat that the final draft be reviewed locally. This task was entrusted, at Galileo's application, to Father Jacinto Stefani, a Dominican.
Riccardi received the preface and conclusion in accordance with this agreement but still stalled, causing Galileo to finally lose patience and refer the matter to the Tuscan Secretary of State (XIV, 217), who brought it to the attention of the Grand Duke. The latter instructed his Ambassador, Niccolini, to move on his behalf, but Riccardi again refused to be rushed. Still more pressure from the Ambassador and his wife resulted in Riccardi proposing much the same compromise as before, except that this time he would send instructions (XIX, 327) to the Florentine Inquisitor, Clemente Egidi, having checked the opening and closing sections himself. Galileo remained deeply frustrated at this performance (XIV, 254) but eventually sent the required passages to Riccardi. Ultimately, Riccardi absolved himself of all responsibility by devolving the decision of whether or not to grant the imprimatur to Egidi. This final permission having at last been gained, printing began and early in 1632 the first copies were ready for sale.
There is no question that Galileo had every right to be annoyed at Riccardi's behaviour, particularly the unprecedented decision to insist on a second revision. Even so, Riccardi—like Niccolini—was aware of the political climate in Rome and how sensitive the publication was likely to be, Niccolini remarking that "the truth is that these opinions are not received well here, especially by superiors" (XIV, 251).
The full title of the work, as insisted upon by Urban VIII, was
Dialogue of Galileo Galilei, Lincean, Special mathematician to the University of Pisa and Philosopher and Chief Mathematician to the Most Serene Grand Duke of Tuscany, where, in the meetings of four days, there is discussion concerning the two Chief Systems of the World, Ptolemaic and Copernican, propounding inconclusively the philosophical and physical reasons as much for one side as for the other...,
abbreviated ever since the 1744 edition as the Dialogue on the two Chief World Systems. The action unfolded over this period of four days as a conversation between Salviati, Galileo's spokesman and (late) great friend Filipo, and Simplicio, named for the sixth century commentator on Aristotle and very much the defender of Aristotelian orthodoxy. The two are joined by Sagredo, the "educated layman between two experts", called after Galileo's best friend during his time in Padua who had died in 1620. A (deliberate) circumstance that would later lead to more trouble for Galileo was the added fact that Simplicio in Italian gives the sense of "simple" or simpleton", and this is indeed descriptive of how he behaved throughout the text.
In his preface, Galileo began by stating that he would show that the decree of 1616 had not had the effect supposed by others (that is, Protestants) and thus proposed "to show to foreign nations that as much is understood of this matter in Italy, and particularly in Rome, as transalpine diligence can ever have imagined" (VII, 29). He went on to say that it would be demonstrated that "all experiments practicable upon the earth are insufficient measures for proving its mobility, since they are indifferently adaptable to a earth in motion or at rest", followed by an examination of "celestial phenomena... strengthening the Copernican hypothesis until it might seem that this must triumph absolutely" and then a look at the tides "from assuming the motion of the earth". All this was ostensibly to illustrate the rationality of the Catholic position as having come about "not from failing to take count of what others have thought" but "for those reasons that are supplied by piety, religion, the knowledge of Divine Omnipotence, and a consciousness of the limitations of the human mind" (ibid, 30); that is, the position of Urban VIII. As we shall see, some of his more important readers were unfortunately not convinced of his sincerity in holding it.
The Arguments Against Galileo (2)
Political issues aside, there remained an excellent and straightforward reason why Galileo had struggled to convince people that the Earth moves: it plainly does no such thing. At that time, common sense gave the lie to Copernicanism in ways that anyone could understand: if the Earth moves, why do birds flying not get left behind? If an arrow is fired straight up into the air, with the Earth spinning at countless miles per hour, why does it fall at (or near) the feet of the firer? Likewise, why does a stone dropped from a tower land at the base, instead of some distance away? This last is the famous tower argument that was considered a total refutation of the motion of the Earth and which Galileo later treated of in the eighth part of the Second Day in his Dialogue, along with its equivalents that involved either dropping a lead ball from the masts of stationary and moving ship and comparing the different landing positions or firing cannons East and West and doing similarly.
In keeping with these common sense objections, a more philosophical counter-argument suggested that reasoning in support of Copernicanism committed the logical fallacy of affirming the consequent. Consider, for example, Galileo's intention to look at the tides on the assumption that the Earth moves. In the course of his discussion, critics said, he proceeded in this fashion:
The Copernican Planetary System
- First Premise: If the Earth moves, we would observe phenomenon x (the tides, say);
- Second Premise: We observe phenomenon x;
- Conclusion: Therefore, the Earth moves.
This is the formal fallacy of affirming the consequent (the basic form being "if P then Q; Q; therefore, P"). In layman's terms, that an hypothesis such as the Earth moving could explain the observations did not imply that it was therefore a true hypothesis, not least because there might be others that could do likewise (as indeed there were, according to those who held to the Tychonic system). A fallacious argument seemed to give no reason to abandon either common sense or the instrumental interpretation of theories.
It was also said that Copernicanism was simpler as a mathematical construct and ought to be preferred on that basis alone. This, of course, is in keeping with the general preference for parsimony or simplicity in theories that has characterised much (but not all) science for very many years (cf. Holton, 1988). Since Copernicus could explain on the basis of geokineticism what the Ptolemaic system could only manage with the addition of a complicated structure of eccentrics, epicycles, deferents and equants, his ideas must be closer to the true picture (if indeed they were to be read realistically) or easy to use. However, Copernicus actually introduced epicycles of his own, and even epicycles on top of these, leading Cohen to exclaim that the notion of Copernicus's system being the simpler should be taken "cum grano salis, in fact, with the whole cellar" (2001: 111). This, in any case, is a modern argument, one that Galileo did not face. In his time, the question of which system was simpler does not appear to have been asked (Cohen, op cit: 116).
Galileo's use of the telescope has caused much discussion, too. As we noted above, many people refused to look through the telescope or, having done so, refused to believe what they saw. Although we may regard the former position as ridiculous, the latter was rather more justified. The telescope was a new invention and to some it must have seemed like magic. How, Clavius asked, could it be known that what was seen was actually there, rather than a trick of the lenses? As Feyerabend (op cit) and Kuhn (1975: 224) have remarked, Galileo had no theory of optics to answer this criticism, so he relied instead on demonstrations. By pointing his telescope at something terrestrial in the distance, observers could verify for themselves that it had shown a true representation of what was there. There was no guarantee, however, that this should hold when the telescope was raised to the heavens. The situation changed somewhat when the Jesuits announced that they had confirmed Galileo's studies with the telescope, but this, too, was merely a useful (albeit powerful) aid and not a proof. The effect of Galileo's public shows was nevertheless such that this objection remains a recent (and philosophical) one, particularly in the reductio form employed by Feyerabend.
Another relatively recent argument frequently used to justify the second of the myths we began with concerns the tides. It is said that Galileo was wrong about what caused them (as we saw above, he eventually agreed that the moon was responsible, although, as we shall see, this is not quite accurate) and his use of them to prove Copernicanism was flawed. That the error lies in the other direction will become apparent shortly but since, in his Dialogue, the first thing Galileo had to do was tackle the appeal to common sense, that is where we shall begin.
Philosophy of Science and the Galileo Affair
On the second day of discussion, Galileo has Salviati remark on another author (Chiaramonti) who had suggested that those who would disagree with the tower argument must see a stone dropped from the top falling not straight down but in an arc:
... in this way he hints at believing that to those who say that such motion is not straight at all, but rather circular, it seems they see the stone move visibly in an arc, since he calls upon their senses rather than reason to clarify the effect. This is not the case, Simplicio, for just as I ... have never seen nor ever expect to see, the rock fall any way but perpendicularly, just so do I believe that it appears to the eyes of everyone else. It is, therefore, better to put aside the appearance, on which we all agree, and to use the power of reason either to confirm its reality or to reveal its fallacy. (Drake, op cit: 126)
Note that Galileo's strategy here was to agree with the common sense view of what happens when a stone is dropped from a tower but to challenge its interpretation; that is, to challenge the "basic epistemological principle ... that under normal conditions the human sense are reliable, that they tell us what is really happening, that normal observation reveals reality to us" (Finicchiaro, 1997: 56). Although circumstances opposing this principle were not new (observing a stick in water to be bent when its removal reveals it to be straight, for example, or the one given by Galileo immediately after the tower argument—that of the moon following us as we walk.), Galileo apparently proposed here to put aside the appearances and place reason as the highest court of appeal. This brought (and brings) up many associated questions: when are our senses reliable? When should the evidence of common observation be rejected? Should we always appeal to reason over observation, or only when there is controversy? How do we demarcate between controversial and non-controversial issues? And so on.
When we read on, we find that Galileo did not in fact propose to supplant one principle with another, instead calling for the use of the senses "accompanied by reasoning" (op cit: 255, italics added). In general, philosophers and historians of science have seemed determined to characterise Galileo's science in one way or another while at the same time contriving to overlook the subtlety in his works. Still on the second day, Galileo sketched the scene of two friends in a ship's cabin, throwing a ball to each other and taking note of the movements of fish, butterflies and the like that happen to be with them. On the first occasion this situation plays out while the ship is at rest alongside; on the second, it is underway. The friends in the former notice no difference in the force needed to throw the ball in one direction rather than another and observe no similar difficulty in the animal sharing the cabin with them. This remains the case, according to Galileo, for the latter, too.
This is the introduction of Galilean relativity, which was relied on much later by Einstein. From the perspective of the friends in the cabin, the motion of the ship relative to land has no effect on the motion of the ball relative to the cabin, since the additional motion imparted to the ball by the motion of the ship is also granted to the cabin. This implied that the stone dropped from the mast of a moving ship appears to fall straight down because its motion in any other direction is shared by the ship—or the inertial frame in modern parlance—so that the observer sees only a straight descent. Likewise, the stone dropped from a tower on a moving Earth is not viewed from an absolute point of reference but relative to the tower and its immediate surroundings, which are (according to the assumption of geokineticism) also moving.
The importance of relativity can scarcely be overstated, but what Galileo was able to do was take an observation that refuted geokineticism, re-describe it, and so turn it into a confirmation of the Earth's movement. This is an example of meaning variance between theories, a concept that would later form the basis of the notion of incommensurability. It shows Galileo not to be rejecting observation on the basis of theory, or vice versa, but using reasoning to invite his readers to consider the evidence of their senses in a new way in support of a different worldview. Any effort to cast him solely as an empiricist or a rationalist, then, is bound to fail.
Another fascinating approach to the motion of the Earth that was discussed by Copernicus and which involved the Aristotelian theory of place, which Aristotle himself had defined as "what contains that of which it is the place" (Physics, IV, 211a). Although Finocchiaro (1997:14) remarked that natural motion "has always been regarded as an essential or defining characteristic of a physical body. This seems to have remained unchanged even by the Copernican Revolution", he failed to realise the importance this held for Copernicus. In the Aristotelian system, the outermost sphere of the heavens was supposed to have a natural motion but it could have no place, since, being uncontained in any further sphere, no place could be granted to it under Aristotle's conception above. Thus Aristotle was left with the unfortunate situation in which the outer sphere had natural motion but no place; and since it had no place it could have no motion, which was defined as a change in place. Max Jammer explained that one consequence was that
... Copernicus finally came to the conclusion that that the two ideas [Aristotelian place and natural motion] were irreconcilable, and that at least one of them would have to be rejected. Either the definition of "place" had to be revised, or the dogma of the motion of the outermost celestial sphere had to be repudiated. As we know, Copernicus preferred the second alternative. (1993: 72-73)
Copernicus’ De Revolutionibus Orbium Celestium
In his De revolutionibus orbium celestium, Copernicus drew attention to this difficulty by saying that "since it is the heavens which contain and embrace all things as the place common to the universe, it will not be clear at once why movement should not be assigned to the contained rather than to the container" (1953: 515), later calling the latter option "absurd" (op cit: 520). That there was no way around this issue was clear to Copernicus in the late sixteenth century but not to philosophers of science in the twentieth, it seems. Whether the Aristotelian concept of place or the fixed Earth had to be rejected, his authority and infallibility could no longer be maintained.
It is well known that Copernicanism was slow to gain a following, with only ten Copernicans noted between 1543 and 1600 (those being Rheticus; Maestlin; Rothmann; Kepler; Bruno; Galileo himself; Digges, Harriot; de Zu iga; and Stevin) (Westman, 1986:85). One of the main (logical) objections to it was that it engaged in circular reasoning. That is, the motion of the Earth was assumed in order to explain phenomena; whereupon the excellence of the explanations was taken to imply the motion of the Earth (more strictly, this is affirming the consequent as before). In the Dialogue, Galileo had Simplicio voice this concern:
I do not think it can be denied that your argument goes along very plausibly, the reasoning being ex suppositione as we say, that is, assuming that the earth does move in the two motions assigned to it by Copernicus. But if we exclude those movements, all the rest is vain and invalid; and exclusion of this hypothesis is very clearly indicated to us by your own reasoning. Under the assumption of the two terrestrial movements, you give reasons for the ebb and flow, and then vice versa, reasoning circularly, you draw from the ebbing and flowing the sign and confirmation of those same two movements. (op cit: 436)
This philosophical criticism is enough to end all possibility of definitively proving Copernicanism. Nevertheless, some philosophers of science have chosen to portray Galileo as a Copernican zealot in spite of his stating plainly—rather than excluding—an objection at the close of his work that would have demonstrated to any philosophically-inclined reader than no such proof was to be found in the book (nor, in principle, could there be). Why would a determined Copernican desperate to convince others of his certainty offer such a decisive refutation of his own position? The question can only be rhetorical. It is hard to see why we should not instead read Galileo as having honestly confronted what he knew would be the main focus of philosophical disapproval, not least because he leaves this criticism unanswered. Indeed, given the contexts already established above, it would seem that his argument was to be a probabilistic one which showed both that the Ptolemaic system was untenable and that the Copernican was at least plausible, if not likely on the balance of the observations and reasoning available. Once again, Galileo the passionate advocate of Copernicanism gives ways to Galileo the prudent defender of his Church.
Supporters of the second myth we began with have looked elsewhere for justification of their reading of the Galileo affair. Another strand has focused on the idea that Bellarmine and the Church correctly rejected Copernicanism as unscientific (cf. Feyerabend, 1993: 126-129—his 2002: 247-264 is a distinct approach to the same question—and Duhem, 1908), with Duhem (op cit, quoted in de Santillana, 1958: 107) asserting that "[l]ogic was on the side of Osiander and Bellarmine and not on that of Kepler and Galileo". Bellarmine's letter to Foscarini of 1615 (XII, 171-172), quoted previously, is typically offered as indicative of his scientific bent, the charge being that while Galileo supposedly wanted unproven theories to be accepted as true, Bellarmine was far more reasonable in stating that Scriptural interpretations should not be changed on this faulty basis and that merely saving the appearances is not enough to render a theory true. This is the third point of the letter, however, and in emphasising it we lose sight of the second:
Consider now, with your sense of prudence, whether the church can tolerate giving Scripture a meaning contrary to the Holy Fathers and to all the Greek and Latin commentators. Nor can one answer that this is not a matter of faith, since it is not a matter of faith ex parte objecti [as regards the topic or object of discussion], it is a matter of faith ex parte dicentis [as regards the speaker]; and so it would be heretical to say that Abraham did not have two children and Jacob twelve, as well as to say that Christ was not born of a virgin, because both are said by the Holy Spirit through the mouth of the prophets and the apostles. (op cit)
Here Bellarmine had given a very different principle, according to which all Scriptural passages were to be taken as coming through the writer directly from the Holy Spirit. Supposing, then, with Galileo, that the motion of the Earth is not a matter of faith because it is an astronomical issue is thus rejected by Bellarmine because the source of the Biblical statements on geostaticism and geocentrism is the Holy Spirit. Any dissent is thus straightforwardly heretical. We see at once that this approach renders Bellarmine's "scientific" remarks in the rest of his letter moot: "If Scripture statements on the motion of the Sun are 'matters of faith' in the sense indicated by Bellarmine, they constituted truths which could not be doubted and which could never be overturned by whatever progress science might make" (Fantoli, op cit: 187). No amount of subsequent investigation could over-rule the fact that the Holy Spirit had declared in Scripture that the Earth did not move—precisely the stance that Galileo was trying to remove because he thought that it would place his Church in a very difficult position (and subject to ridicule) if, as it seemed, Copernianism should be true or, at any rate and with the same consequence, the Ptolemaic system false. To call Bellarmine's position scientific when its rigorous application would have killed science completely is, to be blunt, quite absurd.
Another criticism of Galileo states that he was condemned by his own opinions from his Letter to Christina (for example, Shea, 2003:73-74):
These words imply I think the following doctrine: in the learned books of worldly authors are contained some propositions about nature which are truly demonstrated and others which are simply taught; in regard to the former, the task of the wise theologians is to show that they are not contrary to Holy Scripture; as for the latter (which are taught but not demonstrated with necessity), if they contain anything contrary to the Holy Writ, then they must be considered indubitably false and must be demonstrated such by every possible means. (V, 327)
The lesson here is supposed to be clear: if a proposition is not demonstrated as necessarily true, the Church was quite correct to assert their falsity and use "every possible means" to ensure that this is known to be the case. Galileo, then, could have no complaint. Nevertheless, we need only consider the very next lines of the Letter to see what Galileo had meant:
So physical conclusions which have been truly demonstrated should not be given a lower place than Scriptural passages, but rather one should clarify how such passages do not contradict those conclusions; therefore, before condemning a physical proposition, one must show that it is not conclusively demonstrated. Furthermore it is much more reasonable and natural that this be done not by those who hold it to be true, but by those who regard it as false... (op cit)
This is the eminently sensible idea that a proposition should not be condemned as heretical unless it has been shown to not be demonstrated, thus preventing people from merely declaring Copernicanism to be false in order to have it condemned by the authorities. Moreover, those who would wish to have it condemned should have the burden of proof associated with that claim. This would require that any theologian who wished to see a scientific proposition condemned would have to show that it ought to be, and hence would have to understand it sufficiently to justify his claim that it was not demonstrated to a degree that would imply changing the interpretation of Scripture accordingly. Given the fate that could await the heretic, this is both reasonable and—at the very least—just. Once again, we see that the effort to sustain the second myth can lead to illiteracy.
When Galileo finally came to discuss the ebb and flow of the sea on the fourth day (although this ordering is open to doubt), he was disdainful of the idea that the Moon had a significant influence on the tides. He rejected the supposed attraction between the Moon and Earth as part of his general objection to "occult properties" (VII, 486) and sought a terrestrial, mechanical explanation. Since there was no proof or theory of gravitational attraction at that time, we might expect Galileo to be lauded by mythicists in the second sense for his (Bellarminean) scientific rejection of gravitational explanations of the tides. Instead, he is criticised for having held the incorrect opinion. In fact, there is an effect on the tides caused by the diurnal rotation of the Earth. Moreover, Galileo was well aware of the sheer complexity of the phenomenon and gave many factors that played a part in his theory (Dialogue, 457-462). Thus did Drake observe that "the departure of presentations of Galileo's theory from what he wrote goes ever widening" (1999, 2: 111). That Galileo did not consider his argument a proof of Copernicanism has already been established, but this attempt to justify the second myth remains popular. In short, Galileo's theory was "incorrect but scientific" (Drake, 2001: 93) and modern tidal theories retain a degree of intricacy that renders any attempt to speak of Galileo's as "inadequate" little more than anachronism (cf. Drake, 1999, 2: 107).
Galileo's stated purpose in the Letter, his correspondence and in the Dialogue itself was in any case already being practised by the Church. As is well known, there are Biblical passages suggesting a flat Earth (Daniel 4:11, for instance) that were not interpreted realistically (although Bellarmine's principle would have meant otherwise) and for the Church to insist on a literal reading would have been thought ridiculous, particularly by the Protestants. What Galileo was asking for, then, was neither new nor controversial. This should lead us to a rejection of the first myth, of course, because Galileo did get into trouble all the same.