The following is an excerpt from Ian Hacking's introduction to the new edition of Thomas S. Kuhn's The Structure of Scientific Revolutions, which commemorates the book's 50th anniversary. To be published by University of Chicago Press at the end of this month, Kuhn's book is often cited as one of the most-often-cited books of all time.
ONE THING IS NOT SAID often enough: Thomas S. Kuhn's The Structure of Scientific Revolutions, like all great books, is a work of passion, and a passionate desire to get things right. This is plain even from its modest first sentence: "History, if viewed as a repository for more than anecdote or chronology, could produce a decisive transformation in the image of science by which we are now possessed." Thomas Kuhn was out to change our understanding of the sciences — that is, of the activities that have enabled our species, for better or worse, to dominate the planet. He succeeded.
The present edition commemorates the fiftieth anniversary of The Structure of Scientific Revolutions. Nineteen sixty-two was a long time ago. The sciences themselves have radically changed. The queen of the sciences, then, was physics. Kuhn had been trained as a physicist. Few people knew much physics, but everybody knew that physics was where the action was. A cold war was in progress, so everyone knew about the Bomb. American schoolchildren had to practice cowering under their desks. At least once a year towns sounded an air raid siren, at which everyone had to take shelter. Those who protested against a nuclear weapon, by ostentatiously not taking shelter, could be arrested, and some were. Bob Dylan first performed "A Hard Rain's A-Gonna Fall" in September 1962; everyone assumed it was about nuclear fallout. In October 1962 there was the Cuban Missile Crisis, the closest the world has come, after 1945, to nuclear war. Physics and its threat were on everyone's mind.
The Cold War is long over, and physics is no longer where the action is. Another event of 1962 was the awarding of Nobel prizes to Francis Crick and James Watson for the molecular biology of DNA and to Max Perutz and John Kendrew for the molecular biology of hemoglobin. That was the harbinger of change. Today, biotechnology rules. Kuhn took physical science and its history as his model. You will have to decide, after reading his book, about the extent to which what he said about the physical sciences holds true in the teeming, present world of biotechnology. Add in information science. Add in what the computer has done to the practice of science. Even experiment is not what it was, for it has been modified and to a certain extent replaced by computer simulation. And everyone knows that the computer has changed communication. In 1962 scientific results were announced at meetings, in special seminars, in preprints, and then in articles published in specialist journals. Today the primary mode of publication is in an electronic archive.
There is yet another fundamental difference between 2012 and 1962. It affects the heart of the book, fundamental physics. In 1962 there were competing cosmologies: steady state and big bang, two completely different pictures of the universe and its origin. After 1965 and the almost fortuitous discovery of universal background radiation, there is only the big bang, full of outstanding problems pursued as normal science. In 1962 high-energy physics seemed to be an endless collection of more and more particles. What is called the standard model brought order out of chaos. It is unbelievably accurate in its predictions, even if we have no idea how to fit it together with gravity. Perhaps there will not be another revolution in fundamental physics, although for sure there will be surprises galore.
Thus The Structure of Scientific Revolutions may be — I do not say is — more relevant to a past epoch in the history of science than it is to the sciences as they are practiced today.
But is the book history or philosophy? In 1968 Kuhn began a lecture insisting, "I stand before you as a practicing historian of science. I am a member of the American Historical, not the American Philosophical, Association." But as he reorganized his own past, he increasingly presented himself as always having had primarily philosophical interests. Although The Structure of Scientific Revolutions had an immense immediate impact on the community of historians of science, its more enduring effects have probably been upon philosophy of science and, indeed, on public culture.
"Structure" and "revolution" are rightly put up front in the book's title. Kuhn thought not only that there are scientific revolutions but also that they have a structure. He laid out this structure with great care, attaching a useful name to each node in the structure. He had a gift for aphorism, and his names have acquired an unusual status, for although they were once arcane, some of them are now part of colloquial English. Here is the sequence: (1) normal science; (2) puzzle-solving; (3) paradigm, a word which, when he used it, was rather uncommon, but which after Kuhn has become banal (not to mention paradigm shift!); (4) anomaly; (5) crisis; and (6) revolution, establishing a new paradigm.
That is the structure of scientific revolutions: normal science with a paradigm and a dedication to solving puzzles; followed by serious anomalies, which lead to a crisis; and finally resolution of the crisis by a new paradigm. Another famous word does not occur in the section titles: incommensurability. This is the idea that, in the course of a revolution and paradigm shift, the new ideas and assertions cannot be strictly compared to the old ones. Even if the same words are in use, their very meaning has changed. That in turn led to the idea that a new theory was not chosen to replace an old one, because it was true but more because of a change in world view. The book ends with the disconcerting thought that progress in science is not a simple line leading to the truth. It is more progress away from less adequate conceptions of, and interactions with, the world.
Progress through Revolutions
The sciences progress by leaps and bounds. For many people, scientific advance is the very epitome of progress. If only political or moral life could be like that! Scientific knowledge is cumulative, building upon previous benchmarks to scale new peaks.
That is exactly Kuhn's picture of normal science. It is truly cumulative, but a revolution destroys the continuity. Many things that an older science did well may be forgotten as a new set of problems is posed by a new paradigm. That is indeed one unproblematic kind of incommensurability. After a revolution there may be a substantial shift in topics studied, so that the new science simply does not address all the old topics. It may modify or drop many of the concepts that were once appropriate.
What then of progress? We had thought of a science as progressing towards the truth in its domain. Kuhn does not challenge that conception of a normal science. His analysis is an original account of exactly why normal science is a social institution that progresses so speedily, in its own terms. Revolutions, however, are different, and they are essential to a different kind of progress.
A revolution changes the domain, changes even (according to Kuhn) the very language in which we speak about some aspect of nature. At any rate it deflects to a new portion of nature to study. So Kuhn coined his aphorism that revolutions progress away from previous conceptions of the world that have run into cataclysmic difficulties. This is not progress towards a pre-established goal. It is progress away from what once worked well, but no longer handles its own new problems.
The "away from" seems to call in question the overarching notion of science as aiming at the truth about the universe. The thought that there is one and only one complete true account of everything is deep in the Western tradition. It descends from what Auguste Comte, the founder of positivism, called the theological stage of human inquiry. In popular versions of Jewish, Christian, and Muslim cosmology, there is one true and complete account of everything, namely what God knows. (He knows about the death of the least sparrow.)
This image gets transposed to fundamental physics, many of whose practitioners, who might proudly proclaim themselves to be atheists, take for granted that there just is, waiting to be discovered, one full and complete account of nature. If you think that makes sense, then it offers itself as an ideal towards which the sciences are progressing. Hence Kuhn's progress away from will seem totally misguided.
Kuhn rejected that picture. "Does it really help," he asked, "to imagine that there is some one full, objective, true account of nature and that the proper measure of scientific achievement is the extent to which it brings us closer to the ultimate good?" Many scientists would say that yes, it does; it grounds their image of what they do, and why it is worthwhile. Kuhn was too brief with his rhetorical question. It is a topic for the reader to pursue. (I myself share Kuhn's skepticism, but the issues are difficult and not to be decided quickly.)
Kuhn cannot take seriously that "there is some one full, objective, true account of nature." Does this mean that he does not take truth seriously? Not at all. As he observed, he said nothing about truth in the book, except when quoting Bacon. Wise lovers of facts, who try to determine the truth about something, do not state a "theory of truth." Nor should they. Anyone familiar with contemporary analytic philosophy will know that there are myriad competing theories of truth. Kuhn did reject a simple "correspondence theory" which says true statements correspond to facts about the world. A majority of hard-headed analytic philosophers probably do the same, if only on the obvious ground of circularity: there is no way to specify the fact to which an arbitrary statement corresponds except by stating the statement.
In the wave of skepticism that swept American scholarship at the end of the twentieth century, many influential intellectuals took Kuhn as an ally in their denials of truth as a virtue. I mean the thinkers of the sort that cannot write down or utter the word true except by literally or figuratively putting quotation marks around it — to indicate how they shudder at the very thought of so harmful a notion. Many reflective scientists, who admire much of what Kuhn says about the sciences, believe he encouraged deniers.
It is true that The Structure of Scientific Revolutions gave enormous impetus to sociological studies of science. Some of that work, with its emphasis on the idea that facts are "socially constructed" and apparent participation in the denial of "truth," is exactly what conservative scientists protest against. Kuhn made plain that he himself detested that development of his work. Notice that there is no sociology in the book. Scientific communities and their practices are, however, at its core. There had been sociology of scientific knowledge before Kuhn, but after Structure it burgeoned, leading to what is now called science studies. This is a self-generating field (with, of course, its own journals and societies) that includes some work in the history and the philosophy of sciences and technology, but whose emphasis is on sociological approaches of
various kinds, some observational, some theoretical. Much, and perhaps most, of the really original thinking about the sciences after Kuhn has had a sociological bent.
Kuhn was hostile to these developments. In the opinion of many younger workers, that is regrettable. Let us put it down to dissatisfaction with growing pains of the field, rather than venturing into tedious metaphors about fathers and sons. One of Kuhn's marvelous legacies is science studies as we know it today.
The Structure of Scientific Revolutions was first published as volume 2, number 2, of the International Encyclopedia of Unified Science. In the first and second editions, both the title page, page i, and the table of contents, page iii, said so. Page ii gave some facts about the Encyclopedia; twenty-eight names of editors and advisors were listed. Most are rather well known even fifty years later: Alfred Tarski, Bertrand Russell, John Dewey, Rudolf Carnap, Neils Bohr.
The Encyclopedia was part of a project begun by Otto Neurath and fellow members of the Vienna Circle. With the exodus from Nazism, it moved from Europe to Chicago. Neurath envisaged at least fourteen volumes consisting of many short monographs by experts. It did not get past volume 2, monograph 1, before Kuhn submitted his manuscript. After that, the Encyclopedia was moribund.
The print runs for previous monographs of the International Encyclopedia were for a small group of specialists. Did the University of Chicago Press know it had a bombshell? In 1962-63, 919 copies were sold and 774 in 1963-64. Next year the paperback sold 4,825, and then we never looked back. By 1971, the first edition had sold more than 90,000 copies, and then the second edition — with the postscript — took over. The grand total to mid-1987, after twenty-five years of publication, was just short of 650,000.
For a while people talked about the book as being one of the most cited works about anything — right up there with the usual suspects, namely the Bible and Freud. When at the millennium the media were churning out their ephemeral lists of the "best books of the twentieth century," The Structure of Scientific Revolutions often appeared.
Much more important: the book really did change "the image of science by which we are now possessed." Forever.