A review from the TLS

Revolution in the heavens

David Wootton

Robert S. Westman
THE COPERNICAN QUESTION
Prognostication, skepticism, and celestial order
681pp. University of California Press. $95; distributed in the UK by Wiley. £65.
978 0 520 25481 7

Steven Shapin and Simon Schaffer
LEVIATHAN AND THE AIR-PUMP
Hobbes, Boyle, and the experimental life
New edition 440pp. Princeton University Press. Paperback, $29.95; distributed in the UK by Wiley. £20.95.
978 0 691 15020 8

Published: 19 October 2011

On the night of February 19, 1604, Johannes Kepler was out measuring the position of Mars in the sky with a metal instrument called a quadrant. It was bitterly cold with a biting wind. Kepler found that if he removed his gloves, his hands were soon too numb to manage his instrument; if he kept them on, he could barely make the fine adjustments necessary. The wind was too strong to keep a candle alight, so he had to read his measurements and write them down by the light of a glowing coal. The results, he felt sure, were unsatisfactory – he was out, he thought, by ten minutes of a degree. On a modern school protractor you cannot distinguish ten minutes of a degree, and only one astronomer before Kepler would have thought such a measurement unsatisfactory. The greatest astronomer of the ancient world, Ptolemy, had regarded ten minutes as precisely his acceptable margin of error. But Kepler had worked with Tycho Brahe, who had devised new instruments capable of measuring with unbelievable accuracy, to a single minute.

Kepler was worried about such tiny numbers because he wanted to prove that Tycho’s theoretical tools could not provide an accurate account of Mars’s movement through the heavens – Kepler’s best predictions, using traditional methods, were out by up to eight minutes. By the time Kepler had found a satisfactory way of handling this aberrant eight minutes, he had abandoned the notion that all heavenly movements are circular and introduced the idea of an orbit – the regularly repeated trajectory of an astronomical object through space. This was the culmination of an astronomical revolution that had begun in 1572, with the appearance of a supernova as bright as Venus. According to Aristotle, there was never any change in the heavens, so the nova ought to have been in the upper atmosphere, like a shooting star – but Tycho proved, by measuring parallax (or rather its absence), that it could only be in the heavens. This startling result turned into a large-scale crisis for the old ways of thinking when Tycho’s measurements of the comet of 1577 showed that not only was it in the heavens, but its path cut through the transparent orbs that were supposed to carry the planets – it took Tycho a decade to accept the obvious conclusion that there were no orbs, and that the planets float through space. But not even Tycho could imagine that heavenly movements were anything other than circular.

Kepler replaced orbs with orbits (the word used in this sense was a marker of Kepler’s key innovation – previously an orbit was the track left by a wheel in the ground), replaced circles with ellipses, geometry with physics. He did so even though he came to recognize, reluctantly, that one could give a perfectly satisfactory account of his new measurements using the old apparatus of circles, eccentrics and epicycles. The problem for Kepler was that circles, eccentrics and epicycles were geometrical constructions; there was no evidence that any such gearing existed in the heavens. In order to understand the movements of the planets, Kepler thought about ferrymen trying to row across a fast-flowing river. If you were steering a planet through space, he wondered (for Kepler was prepared to imagine intelligences guiding the planets), how would you locate yourself, and how would you keep on course? An eccentric, which involved a perfect circle around an unmarked point in featureless space, seemed to him an impossibility. The celestial orbs, which had been perfectly plausible to Copernicus, had been destroyed, and so now one had to think about forces flowing through space – Kepler’s inspiration was provided by the Englishman William Gilbert, who had published an experimental study of magnetism in 1600 – and ask oneself how a celestial helmsman would take his bearings.

When Kepler published his New Astronomy Based Upon Causes, or Celestial Physics (the subtitle, usually omitted, is important – this is a physical astronomy, not a geometrical astronomy) in 1609, there were three contending systems of the world: the geocentrism of Ptolemy, the heliocentrism of Copernicus and Kepler, and the geo-heliocentrism of Tycho. A year later, Galileo discovered the phases of Venus, and thereby killed off the Ptolemaic system. But the Tychonic system long remained a viable contender. In 1651, Giovanni Battista Riccioli published his Almagestum novum, a magisterial summing up of the long debate provoked by Copernicus’s De revolutionibus (1543). The Catholic Church had condemned Copernicanism in 1616 and Galileo in 1633. Now Riccioli set out to show that the Church was right. Or did he? Riccioli was a Jesuit, bound by obedience, but some historians have suspected him of having secret sympathies with his opponents. How could a man so clever and so learned fail to see the strength of the arguments for Copernicanism? It seems unlikely that Riccioli had private doubts, for he had no difficulty amassing a vast body of argument in favour of the geo-heliocentric system. When Riccioli weighed the Copernican and Tychonic systems in the balance (as he did in the frontispiece to his volume), the scales tipped decisively in favour of a stationary earth at the centre of the universe. As for Ptolemy’s system, which had reigned unchallenged for 1,400 years, it now lay discarded. The Tychonic system was only finally killed off by Newton’s theory of gravity; by the early eighteenth century even the Jesuits were teaching Copernicanism.

This long century from Copernicus to Riccioli, when the fate of Copernicanism hung in the balance, is Robert S. Westman’s subject. Back in 1957, Thomas Kuhn published his first book, The Copernican Revolution. The book had taken him, from beginning to end, eight years at most to research and write. Five years later came The Structure of Scientific Revolutions. By 1971, when Westman completed his PhD on Kepler’s adoption of Copernicanism, it was clear that Kuhn’s first book was overdue to be displaced by something more learned and more historical. And so Westman set to work. In 1986 a book entitled The Copernicans was described as forthcoming. But the project grew and grew: in 1991 Westman embarked on a whole new study of Copernicus’s intellectual formation. By 2005 he had a complete draft. And now, more than forty years after he began work, twenty-five years after he announced the book as forthcoming, twenty years after he decided his first project was insufficiently ambitious, six years after he came to a sort of a stop (for it is clear that Westman stopped reading systematically in 2005 – my discussion of orbits above, for example, is based on an article by Bernard R. Goldstein and Giora Hon, published in that year, which Westman does not cite) – now, at long last, we have this vast (and beautifully produced and illustrated) book to hold in our hands.

A book so long in the making is itself an embodiment of history. It began – and was almost completed – as the study of a scientific revolution which occurred in slow motion. Kuhn, it turns out, was wrong. His theory was that a scientific revolution is always a response to an intellectual crisis. But Copernicus neither responded to nor brought about a crisis in orthodox astronomy. In the first fifty years after the publication of his book only two competent mathematicians defended Copernicanism as a cosmology in print – Copernicus’s sole disciple, Rheticus, and the Englishman Thomas Digges. Experts read and annotated their copies of Copernicus, but the heliocentric hypothesis was in their view the least interesting part of the book. What they were interested in were the new tools that Copernicus provided for geometrical astronomy. Even Kuhn recognized that “the success of the De revolutionibus does not imply the success of its central thesis”. Astronomers were happy to employ and revise Copernicus’s tables for predicting the positions of planets in the heavens. This did not make them Copernicans; it just showed that they were keen to get their facts straight. The real crisis in astronomy came, as we have seen, much later, with the nova of 1572, the comet of 1577, and Galileo’s telescopic discoveries. It was new facts which destroyed the Ptolemaic system, not Copernicus’s peculiar hypothesis.

Kuhn, of course, would have found these arguments unpalatable. According to him, facts are always tightly enmeshed in theories, and never able to break free and assert their independence. The theory-dependence of facts meant, in Kuhn’s view, that proponents of different systems would always be unable to agree about the meaning of a fact. A mere measurement should not be sufficient to destroy a whole intellectual system. In 1957 his position was at first sight more conventional: “trustworthy, extensive, and up-to-date data are Brahe’s primary contribution”, he wrote, and these, it seemed, were crucial “in leading his contemporaries toward a new cosmology”. Nevertheless, celestial orbs, and the parallax measurements that destroyed them, make only a fleeting appearance in his story. And, despite momentarily acknowledging the importance of the new data, he went on to insist that it really made no difference: what was important was not a new preoccupation with precision but the new questions posed by Copernicus. Kuhn could not accept that it was only once it became clear that the heavenly bodies floated unsupported in space that all sorts of new theories became plausible, including Copernicanism itself.

So Westman started out writing a book that engaged with Kuhn but put back the date of the astronomical revolution by more than fifty years, from 1543 to 1609. Such a book would still be timely, for it would show that theory change was in large part driven by observation and by evidence. But then, in 1991, Westman grasped something that should have been obvious all along, but was not – it had already occurred, it must be said, to Kuhn. In the sixteenth century, astronomy and astrology were two aspects of a single discipline – astronomy was the theory, astrology its practical application. All astronomers were also astrologers, and so Copernicus, when he set out to reform astronomy, must also have intended to reform astrology. This line of inquiry, Westman says, “took on a life of its own”, and he set out to rediscover Copernicus’s links to astrology. The enterprise was problematic because in his publications Copernicus never mentions astrology, but the principle was surely correct – Digges, Tycho and Kepler also took it for granted that the core purpose of the new astronomy was the reform of astrology, and Copernicus certainly learnt his astronomy from astrologers. Kuhn, having briefly raised the question of Copernicanism and astrology, dropped it because he was convinced that Copernicus had never cast horoscopes – which may or may not be true. Westman makes a convincing circumstantial case, at any rate, for thinking that he assisted with their production and interpretation.

In taking astrology seriously, Westman was responding to the post-Kuhnian phase in sociology of science, initiated by David Bloor and Harry Collins, which refused to take it for granted that we know what science is or where its boundaries lie (Collins, for example, worked on parapsychology, studying it exactly as if it were a science). The claim that there is no boundary, and so “good” theories have to be studied in precisely the same way as “bad” theories, came to be known as the Strong Programme. This approach received classical expression in Steven Shapin and Simon Schaffer’s Leviathan and the Air-Pump (1985 – now reissued). Shapin and Schaffer set out to destroy the mystique surrounding science by arguing that Boyle’s air-pump experiments had never “demonstrated” the existence of a vacuum, the very possibility of which had been denied, not only by Aristotle, but also by Descartes. Boyle’s pump always leaked, so there never was a vacuum within the glass sphere. Crucially, Boyle’s experiments could not be successfully replicated – when Huygens tried the “void in a void” experiment, where a barometer was introduced into a vacuum, the level of the mercury failed to fall. The evidence produced by experimental science, Shapin and Schaffer argued, was malleable and problematic, and was only convincing for those prepared to defer to the authority of particular scientists. Boyle claimed to be producing new facts, but his facts were eminently contestable, as Hobbes realized – hence the “Leviathan” of their title. In place of Kuhn’s studies of paradigm shifts they offered an account of science in which questions of knowledge and practices of inquiry were (as Hobbes had claimed) always inseparable from questions of authority and forms of social ordering. In their own preferred formulation: “Solutions to the problem of knowledge are solutions to the problem of social order”. The success of a new theory depended on people’s willingness to adopt the lifestyle that went with it. History of science became relativistic and multicultural. Scientists were thought of as belonging to “communities”, each community with distinctive practices and values. Intellectual change required a social history.

Westman was right to take astrology seriously. But recognizing that astronomy and astrology were the same discipline seen from two viewpoints quickly brings us to an unasked and unanswered question: when, where and why did astronomy and astrology part company? Westman’s assumption seems to be that this story lies outside the scope of his book, although he notes in passing that in 1585 the great Jesuit astronomer Clavius dismissed astrology out of hand; Westman has not realized that in 1611 Galileo (who had been both a practitioner and a believer, but was now seeking an alliance with the Jesuits) also turned against astrology. The link between astronomy and astrology could no longer be taken for granted. Westman also overstates the influence of astrology in the sixteenth century. Guicciardini, for example, appears here as someone who used prognostications uncritically in his history – which is true enough, but in his private reflections he shows himself to be a thoroughgoing sceptic, so the prognostications were evidently there only to entertain his less sophisticated readers.

In other respects, though, Westman was never taken in by the new consensus that formed around the Strong Programme. What structure of authority, what form of life did the supporters of Tycho Brahe (Tycho a Danish nobleman, Riccioli an Italian priest) have in common? What common lifestyle was shared by Digges (a servant of Elizabeth I) and Kepler (a servant of Rudolph II), Galileo (a Florentine) and Descartes (a Frenchman living in Holland), Copernicus’s disciple Rheticus (a Protestant) and Galileo’s disciple Castelli (a Benedictine monk)? Westman’s answer to this is clear and convincing: Copernicanism did not spread as the result of a cultural or social transformation. Its history cannot be written as cultural or social history. Theories had, as Kuhn thought, a life of their own – and so, we may add, did facts.

But how then are we to understand the astronomical revolution, if the great Copernicans have so little in common – if Galileo, for example, complained that he could not even bear to read Kepler, he found his mental processes so alien? In 1979, Elizabeth Eisenstein argued that it was the printing press that made possible Copernicanism in particular and the Scientific Revolution in general. As an argument about De revolutionibus, this is mistaken. But the comet of 1577 provoked more than 180 publications discussing its significance; and Tycho’s great book on the subject provided not only his own measurements of the comet’s parallax, which placed it firmly in the heavens, but an extended review of the measurements and arguments of others. Thus the printing press took scattered astronomers and astrologers, belonging to different cultures and holding varied intellectual commitments, and brought them into a market place of ideas. Kepler, interestingly, dated the moment of transition not to the Gutenberg Bible (1454) nor to Copernicus’s De revolutionibus (1543), but to 1563. Why 1563? His reasoning was astrological: the great planetary conjunction of that year had transformed the world of learning; certainly it had led to a flood of astrological publications. My preferred date would be 1564, the very next year, which saw the first published catalogue of the Frankfurt book fair.

The book fair encapsulates the growth of an international trade in books, what the Jacobean poet Samuel Daniel called “the intertraffique of the mind”. In 1608, Galileo came across a book in the fair’s catalogue whose title was De motu terrae, and naturally tried to get hold of a copy – two years later he was still trying to track one down, appealing to Kepler for help. It is not surprising the Venetian booksellers had been unable to help Galileo, as I cannot find De motu terrae in the Frankfurt catalogues either; but the book exists, so Galileo must have seen it listed in some other catalogue. Had he obtained a copy he would have been disappointed, as its subject is earthquakes, not Copernicanism. At the end of his life, the same international trade meant that Galileo could find a publisher, Elsevier, for his Two New Sciences, the manuscript of which had been smuggled out of Italy, and which was published in Leiden, not in Latin or Dutch, but in Italian, just as the illustrated edition of Thomas Harriot’s Brief and True Report of the new found Land of Virginia (1590) was published in Frankfurt, despite the text being in English.

Markets do not always work for the best – according to Gresham’s law, for example, bad money drives out good: but at the Frankfurt book fair, year by year, slowly but surely, good facts drove out bad. When Kepler published the Rudolphine tables in 1627, based on Tycho’s measurements, and named after their deceased patron, Rudolph II, no one disputed that they were superior to anything that had gone before. Thus the printing press strengthened the hand of the innovators by making it possible for them to pool information and work together. It replaced the professorial lecture, the voice of authority, with a text in whose margin you could scribble your dissent. And, by fostering a constant clash of arguments and ideas (Riccioli against Copernicus; Hobbes against Boyle), it forced each side to adapt and change. What the printing press did, quite simply, was weaken authority and strengthen evidence. One of Galileo’s opponents, Lodovico delle Colombe, protested that Galileo was undermining the monarchy of Aristotle, and with it the principle of monarchy itself – while Galileo and his supporters wrote of a republic of letters and of the learned (repubblica scienziata). Over and over again we find the new scientists adopting their motto from the second-century Platonist Alcinous, “philosophizing wants to be free”.

The printing press also fostered a sort of intellectual arms race where new weapons (the astronomical sextant, invented by Tycho; the telescope, improved by Galileo; the pendulum clock, invented by Huygens – astronomical measurements are worthless without accurate timekeeping) were constantly being brought up to the front line. It’s not surprising that Kepler’s New Astronomy is full of military metaphors – indeed he presents the whole book as a war over the motions of Mars. Riccioli’s book puts vast arrays of evidence and argument to the test, evidence and argument largely generated within Riccioli’s lifetime, and assembled from Paris and Prague, from Venice and Vienna, from books with nothing in common other than that they had all passed at some point through the Frankfurt book fair. Such a book is simply inconceivable within a manuscript culture.

The Eisenstein thesis has never been popular with historians. Westman holds back from it, although he produces plenty of evidence in support of it. Historians like microhistories, not macrohistories. Quite properly, they have insisted that manuscript culture ran alongside print culture – Tycho had an extended network of correspondents, and he tracked down individual copies of De revolutionibus because he wanted to read the annotations written in them by their previous owners. But he also had his own printing press, and after he died Kepler saw Tycho’s unpublished works into print. Indeed, Kepler gave the printing press a prominent place in the frontispiece to the Rudolphine tables, which celebrated the progress of astronomy from the ancient world to the modern era.

“Fact”, not “print”, is the key word in Leviathan and the Air-Pump – the air-pump is presented as a device for the production of “facts”, and Boyle’s publications are described as a technology for making his “facts” credible (let’s leave to one side the minor inconvenience that this crucial word does not appear in Boyle’s New Experiments of 1660). The postmodern scare quotes are appropriate, because Shapin and Schaffer do not share Boyle’s belief in facts. They are quick to seize on Huygens’s difficulties in replicating Boyle’s “void in the void” experiment, to which they devote a long chapter. So keen are they to undermine the reliability of facts that they choose to slide over (you can see the slide on p85 of both the new edition and the old) some crucial evidence, all of which had been laid out in an article by Charles Webster, which they had read.

Boyle’s “void in the void” experiment was merely a reworking, with his new air-pump apparatus rather than Torricellian tubes containing mercury, of an experiment invented by Adrien Auzout, and reported first by Gilles de Roberval and then by Jean Pecquet. Pecquet’s work was translated into English in 1653 (though Shapin and Schaffer do not seem to have consulted it), and was undoubtedly the source of Boyle’s concept of “the spring of the air” (though Boyle is less than frank about his debt to Pecquet). Nobody ever had any difficulty replicating Auzout’s experiment as reported by Pecquet – Henry Power and the Accademia del Cimento provide two examples. Boyle, who carried out conventional vacuum experiments before constructing his air-pump, may have replicated it himself. So when Boyle found himself caught up in a dispute with Huygens over his “void in the void” experiment, he had crucial information that he may have been reluctant to advertise (for it would have involved acknowledging that his own work was much less original than he had implied) but that is essential for understanding his unshakeable confidence that Huygens was wrong and he was right: he knew for certain that the principle underlying his experiment had been tested many times and was perfectly sound.

To devote a very substantial part of their book to Boyle’s and Huygens’s “void in the void” experiments and never to lay out the prehistory of those experiments seriously misleads the reader. But Shapin and Schaffer had no choice: they wanted to argue that Huygens could easily have been right, and Boyle could easily have been wrong, so they had to slide past the evidence that “void in the void” experiments were unproblematic, almost routine. Moreover, any discussion of Auzout, Roberval and Pecquet would have taken them away from their local history of England in the 1660s, their tight-knit community of scientists struggling to establish consensus in the aftermath of the Civil War. It would have radically undermined their claim that knowledge depends on a local culture, for what did Boyle, a Protestant and an alchemist, have in common with a Catholic anatomist like Auzout or a mathematician like Roberval?

There was a similar obstacle preventing them from engaging in any discussion of the history of the idea of the fact. Here Shapin and Schaffer had no ready-made source like Webster to tuck away in their footnotes. It was only a few years later that Barbara Shapiro set out to remedy the gap to which their book drew attention, but she made the basic mistake of thinking of facts as fundamentally English, not noticing that Galileo was happy to write about getting the facts straight, and so, even earlier, was Montaigne. As the word “fact” (not in its old legal sense of a deed – a sense still used in the phrase “accessory after the fact” – but in its new sense, of an objective reality caught in words) entered the English language in the mid-seventeenth century, it had to be glossed so that readers would understand it. The standard gloss was a Greek phrase, familiar to all who had been educated in the philosophy of Aristotle, to hoti, that which is. The Latin gloss was more suprising: res. We still say “the facts speak for themselves” where the Romans said res ipsa loquitur.

Kepler did not have the word “fact” (he wrote of phenomena, observations, effects, experiments, of to hoti), but he certainly had the idea. He chose to place on the title page of his Stella nova (1606) the image of a hen pecking around in a farmyard, with the motto grana dat e fimo scrutans (“hunting about in the crap, she finds grain”). He presented himself not as a great philosopher, but as someone prepared to grub around for facts. And because he had to make his facts credible, he was obliged to adopt many of the techniques that Shapin and Schaffer think are new with Boyle – the apparently prolix recounting of irrelevant details (the glowing coal by which he read his instruments on the night of February 19, 1604), the determination to report failures (Kepler presents his war on Mars as an almost endless series of defeats) with the same care as successes, the insistence on involving the reader as if he were really present. In the Stella nova he even introduces us to his wife, as though we were visiting them at home, explaining that he had found it difficult to refute the arguments of the Epicureans, who thought the universe was the product of chance. But his wife is a more redoubtable adversary than he is:

“Yesterday, when I had grown tired of writing and my mind was full of dust motes from thinking about atoms, she called me to dinner and served me a salad. Whereupon I said to her, if one were to throw into the air the pewter plates, lettuce leaves, grains of salt, drops of oil, vinegar and water and the glorious eggs, and all these things were to remain there for eternity, then would one day this salad just fall together by chance? My beauty replied ‘But not in this presentation, nor in this order’.”

(I have modified Westman’s translation.) So much for what is known as the infinite monkey theorem.

Shapin and Schaffer began work after Westman, but finished long before him. They met in March 1980, and the book was finished by January 1985. If his book encapsulates the history of science since Kuhn, theirs was the product of a singular intellectual moment. The moment is symbolized by their epigraph from Gabriel García Márquez’s One Hundred Years of Solitude: there is an implicit homage, in this mixing of strange fact and stranger fiction, to Michel Foucault’s The Order of Things, which begins with a quotation from Jorge Luis Borges. One might well call their book “magical realist”, for it sets out to subvert our assumption that science provides reliable knowledge and to overthrow our conviction that we know how the world works. Indeed, in the circles in which they moved, magical thinking had become entirely respectable: Harry Collins immersed himself so deeply in parapsychology that he came to believe, at least for a while, in retroactive psychokinesis (“mind over matter acting backwards in time”). In such a world, facts are not only a word we use for our beliefs; our beliefs make facts, just as the children in Peter Pan give life to fairies. Some of Collins’s respondents (and perhaps Collins himself, at least for a while) thought that subatomic particles such as quarks had been brought into existence (literally not metaphorically) by the beliefs of scientists. When Shapin and Schaffer assert that “it is ourselves and not reality that is responsible for what we know”, they appear to acknowledge the existence of reality, but, by denying it any role in the construction of knowledge, they identify science with magic (which really is unconstrained by reality) on the one hand, and with morality (where the category of “responsibility” really does apply) on the other. Of course, if retroactive psychokinesis actually worked, we really would be responsible for what we know.

Westman’s book would have been crisper and sharper if it had been written as a reply to Kuhn, or as either an endorsement or a refutation of the Strong Programme. But one can only admire his long struggle not to be confined by yesterday’s questions. It would have been easy for him to write a good book (The Copernicans was surely that) – but he always wanted to write a still better one. Shapin and Schaffer’s methodological commitments, unfortunately, make it impossible for them to talk of progress, so they cannot ask, in their new introduction, if they would write a better book now. What is more surprising is that they do not discuss the ways in which they might now write a different book. They do not engage with their critics, or even acknowledge their disciples. Instead, they look forward to the day when Leviathan and the Air-Pump is, like the typewriters on which it was written, consigned to history. Even they realize that it is time to move on, but they have no idea how. It is as if they are characters in a Borgesian story in which an author struggles to write a book he has already written. Where Robert Westman successfully wrote The Copernicans over again, Steven Shapin and Simon Schaffer are trapped in a nightmare from which they cannot escape: they are doomed for all eternity to be first Miguel de Cervantes and then Pierre Menard.

David Wootton is Professor of History at the University of York and the author, most recently, of Galileo: Watcher of the skies, 2010.