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Science Turned Upside Down

Revolution in Science

by I. Bernard Cohen
Harvard University Press (Belknap Press), 711 pp., $25.00

The word “revolution” first brings to mind violent upheavals in the state, but ideas of revolution in science, and of political revolution, are almost coeval. The word once meant only a revolving, a circular return to an origin, as when we speak of revolutions per minute or the revolution of the planets about the sun. As a political metaphor, a revolution could, in that sense, mean only a return to better times, or to the true constitution, a ridding of excess or usurpers. The transition to our modern idea was made with the Glorious Revolution of 1688, which made Parliament supreme in England and brought in a Bill of Rights. Yet it could be called a revolution, in those days, partly because of the old sense of the word: the traditional rights of Englishmen had been returned to them. A century later the American and French revolutions were definitive breaks with the past, irreversible establishments of a new order, but even in those cases there was a lingering sense of return. The original rights of man had been restored.

Revolution in science parallels these developments. At the time of the Glorious Revolution there was some rather inconsequential talk of the new science of the seventeenth century being revolutionary. A century later Lavoisier—progenitor of modern chemistry—confidently and unself-consciously proclaimed that he and his peers had effected a revolution. This was a truly irreversible change, and not a return to some older knowledge. It is possible to argue that our present conception of revolution was staked out more securely in science than in political action.

Despite a certain amount of rhetoric, such as “the second American Revolution,” there is a fair consensus about which events in the affairs of a people can rightly be called revolutions. It is also clear that such revolutions are proper objects of study for the historian. In science, however, the label of “revolution” has been so taken up by public relations that any innovative design for an aircraft wing, or technique for splicing genes, is hailed as revolutionary. The merely novel is hyped into a revolution. If we resist such exaggeration we will settle on the work of certain scientists as revolutionary: Copernicus, Darwin, or Einstein, for example.

But it is not evident that revolution should be as interesting in the history of science as in the history of nations. The French Revolution was important because it was a revolution. Darwin was important, but being revolutionary is hardly what makes his contribution to science important. One can even begin to wonder whether to call an event a revolution in science is merely to give an honorific award, like a knighthood or a Nobel prize. Not surprisingly, “revolution” was not a term used in an analytic or theoretical way in the history or philosophy of science until after the Second World War. Since then, however, it has been a central part of a dialogue, or confrontation, between two very different approaches. One is evolutionary and continualist. The other is revolutionary or cataclysmic.

Most scientists and lay people unreflectively have the evolutionary attitude. Certainly at the time of Lavoisier, there were rapid changes in chemistry. Burning had been understood in terms of an imponderable substance called phlogiston; in the 1780s it became well understood that there is no such thing, and that a newly discovered substance, named oxygen, was the key to combustion, breathing, and bleaching. Acids had long been known: now oxygen was (wrongly) taken as the defining component of acids. Even more important, there arose a clear understanding of the difference between chemical compounds (such as iron oxide or carbon dioxide) and mixtures (such as bronze or air). But, the continualist adds, although these changes were rapid enough to merit the praising word “revolution,” they are part of a larger evolution, and differ only in pace, and not in kind, from other developments. Oxygen had been isolated by at least two investigators before Lavoisier. The conceptions of element, compound, and mixture have a long and sometimes painful history.

The chemical revolution of the 1780s, on this view, was simply the rapid fruition of one group of ideas and techniques. Some of it was permanent, while other parts of it needed firm correction (e.g., the account of acidity). It certainly commenced a period of less sensational progess into the inorganic compounds, followed, in the latter part of the nineteenth century, by bold leaps of understanding, analysis, and synthesis of organic compounds, which involve carbon and are the substance of life itself. The dramatic events of the past thirty years in molecular biology are part of the ongoing story—a story of overall progress, of building on the discoveries of our predecessors.

This comfortable view of the growth of knowledge has an iconoclastic and cataclysmic counterpart. Science, it is proposed, grows by fits and starts. There are periods of routine learning that run into some sort of block. The only resolution is a wholesale revision of assumptions and concepts. Lavoisier did not merely advance upon his teachers. He transformed the way in which his group of coworkers (and their successors) think of the world. Earlier descriptions of burning came to be regarded less as false than as unintelligible. Scientific revolutions are just those breaks in knowledge that reorganize our vision of some aspects of the world—reorganize it to such an extent that we can no longer see the world in the old way. Moreover, according to a strong version of this point of view, such mutations in thought are not peculiar to singular heroes such as Lavoisier, Darwin, or Einstein. They are common in the numerous subdisciplines. Radical cuts with the past are perhaps essential to any long-term inquiry that is not to be trapped in scholastic doldrums.

Note, incidentally, that the word “revolution” is not needed to express this point of view. I’ve just spoken of breaks, cuts, and mutations, all words put to such a use in the Thirties by the prolific French philosopher of science and of aesthetics, Gaston Bachelard. They are now the standard terms for French writers, with coupure, in numerous schools, being the word of choice. “Revolution” is, however, the word for debating such issues in English, and there is a history to that which I shall soon describe.

It is perfectly natural to be eclectic between the evolutionary and revolutionary attitude, but a number of vigorous writers align themselves one way or the other. These include both working scientists and observers such as historians or philosophers or science writers. If we were to appoint an arbitrator to help us decide where the truth lies, we would first want a magisterial survey of all the different examples of revolution in science, so that we could think about their frequency, their centrality, and their structure. That is one of the promises of I.Bernard Cohen’s book. It might seem, from a look at its table of contents, that every plausible candidate for a revolution in science since the Renaissance will receive its due. Moreover Cohen presents himself as a historian, uncommitted to this or that philosophical position, but determined to display the historical evidence that is of interest.

Revolution in Science is a cornucopia of information, some familiar, some arcane, part of the knowledge accumulated by one of our most distinguished and most versatile historians of science. He is not one for cataclysms in knowledge, but he is no foe of novelty. He has just reissued a book first published in 1960, The Birth of a New Physics, an important account of the transformation of science from Aristotle to Kepler, and of how that set the stage for Newton.1 The new edition adds some fifty pages of supplements to the former text of 150 pages. Some of these are technical, while others are elaborations of such themes as “What Galileo ‘saw’ in the heavens.” Cohen’s favorite scientist is Newton, whom he sees as revolutionary; indeed his most recent volume about the man appeared in 1980 as The Newtonian Revolution, with Illustrations of the Transformation of Scientific Ideas.2

Like Cohen’s numerous other books, those two fix on a single limb of science. Revolution in Science addresses the entire body. There is nothing else like it for a panorama of what people have chosen to call revolutionary in science. It is also immensely rich in erudition, pleasantly and casually presented in 472 pages of beautifully printed text; almost one hundred pages of more finely printed supplements, and over fifty pages of notes. Weighty, yes, but the material is not in the least oppressive.

The title of the book is significantly not “Revolutions in Science,” an imagined work that might have chapters on Copernicus, Harvey, Galileo, Freud, Einstein, and so forth. Such a book would chiefly tell us what these men achieved. But no, the title is “Revolution in Science.” It is about the idea of revolution in science. The book is a triple-decker. On the first deck are some scientific revolutions, some associated with the names I’ve just listed, and Lavoisier too. On the second deck there are people who describe those events as revolutions. Thus we learn how Lavoisier himself wrote of a revolution in chemistry, and we learn how subsequent writers of different kinds did likewise. Finally on the third deck, or perhaps the bridge, stands Cohen, describing how people described events in terms of revolution.

Cohen provides criteria for recognizing an event as a revolution, but his procedure is curious. He does not primarily give first-deck criteria, at the level of the revolutions themselves, but second-deck criteria, based on whether or not various kinds of people called an event a revolution. He calls four kinds of witnesses. These are (1) scientists contemporary with the event—none better than the very creator of the event, such as Lavoisier in the case of chemistry; (2) later scientific documents in the same discipline—and Lavoisier’s heirs do indeed speak of a revolution in chemistry; (3) historians past and present—once again, these concur that there was a chemical revolution in the 1780s; (4) present scientific tradition in the same field, so that a reflective chemist may be asked whether Lavoisier’s work was revolutionary.

When all four kinds of witnesses agree in calling an event a revolution in science, Cohen is sure that he has located a revolution. There is something strange about this. We do not determine whether there has been a national revolution by asking whether various witnesses call it a revolution. It is instructive, for example, that there is talk of a “quiet revolution,” said to have occurred in Quebec during the past quarter century. But if one wanted to argue that there had been a revolution, one would cite, perhaps, the fact that in a single generation the birth rate dropped from virtually the highest in the world to virtually the lowest, thus suggesting a striking change in the life of the family. If enough interconnected items like that can be presented, we may decide in favor of there having been a quiet revolution. Conversely, if we cannot find such phenomena we will conclude that talk of a quiet revolution is just the hyperbole of journalists and speech writers. The event itself determines whether it is worth calling a revolution, or so we think.

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    Cambridge University Press.

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