To cause a fuss through the sheer force of an idea is, in itself, remarkable. Thomas Kuhn has done something more remarkable: He has caused a fuss that will be 20 years old in October and shows no sign of subsiding any time soon.
He did it by writing a book, "The Structure of Scientific Revolutions," which has been called "a landmark in intellectual history" and "the most important statement written about the scientific enterprise in this half century." It has also been called "completely discredited" and "brilliantly wrong." Along the way, it has inspired two international scholarly conferences and a raft of commentaries and counterworks, sold half a million copies in hardcover and paperback, and been translated into 16 languages including Serbo-Croatian.
At 59, soon to be 60, Kuhn is happily installed as a professor of philosophy at M.I.T. with a modest teaching load and the freedom to think, write and, when necessary, repair to Cape Cod. But being the the central figure in a major intellectual controversy has its hazards as well as its rewards. You can get buffeted around--and not only by people who understand your concepts and dispute them, but by people who misunderstand them and revere them.
In Kuhn's case, a single word, "paradigm," has played a large part in this--and he assigns himself a large share of the blame. "I am the first of the people who misused the word," he says. "It got used in two quite different ways--both of them by me."
But it got used still more loosely by others. Kuhn had been writing about the role of tradition and orthodoxy in science, about how a certain discovery--Lavoisier's of oxygen gas, for example--can set a thinking pattern for the scientists who follow in its wake. Many of Kuhn's readers, however, took his "paradigm" to mean almost any conceptual bond joining almost any group together. Hence social scientists, anxious to win greater respect for their fields, said (in effect), "Now that we know what a paradigm is, all we really need to do is to decide what ours is and enforce it." And student revolutionaries said, "Thank you so much for telling us about paradigms. Now that we know what they are, we can do without them."
"I am told with some authority," says Kuhn, "that there was a period when Kuhn and Marcuse were heroes on the campus of San Francisco State--and we make very strange bedfellows.
"I sometimes think that I like my critics better than my fans," he adds wistfully.
But with the passage of time, he has begun to entertain the hope of being better understood by both critics and fans. Toward that end, he is planning a new book that will delve further into the nature of scientific traditions and scientific communication. Toward that end, too, he sat down for an extended interview in between the National Academy of Science meetings that recently brought him to Washington.
"I don't know if people are still brought up on the story of Galileo and the Leaning Tower of Pisa," says Kuhn, his back to the window of a spacious room at the River Inn, panoramically overlooking the better part of Foggy Bottom. "But it was standard in my day. One was told that Aristotle and his successors used to believe that bodies fell at a speed proportional to their weight, and that Galileo climbed the Tower of Pisa to try this out, and he dropped a wood ball and a lead ball--there are paintings in which he's shown doing this--and discovered that they hit the ground at the same time."
Aristotle, in short, was a hazy-minded philosopher who didn't have the common sense to climb the nearest tall building and try a simple experiment--an experiment that could have spared the world a 2,000-year wait for the scoop on falling bodies.
The problem with this account, according to Kuhn, goes beyond the lack of evidence to support any actual journey up the Tower of Pisa. The problem is a basic misreading of the personalities involved. "If you look at Galileo's written texts on this one," he says, "he doesn't get it by experiment. Galileo in fact does most if not all of the work toward his law--that things fall in a vacuum at the same speed--by what are called 'thought experiments.' What he says about this one--I'll give you a slightly simplified version of it--is, 'Look, imagine that you have two pieces of the same substance, equal size and equal shape. If you let them drop, they'll fall side by side. They're just the same. No reason why one should be ahead of the other. Now tie them together. Well, to conceive them as one body rather than as two bodies is not going to change anything, so here's a body twice the size falling at the same rate as one once the size.' And you can go on to half the size and three times the size."
The Pisa story is unfair to Aristotle besides, says Kuhn. Aristotle's notions about motion were "much more complex" than he is generally given credit for, and he was "quite a shrewd observer himself. His theory fits everyday observation much better than Galileo's does . . . I mean the Galilean law of falling bodies applies in a vacuum. Nothing ever falls in a vacuum. You drop a heavy body and a light body--a piece of paper and a book--and even if you crumple the paper a little before you drop it, the book will get to the ground way ahead of the paper."
When he began delving into matters Galilean, Kuhn was a mere graduate student going for his PhD in physics. In 1947, James B. Conant, the chemist and president of Harvard University, had asked Kuhn to help teach a course in science for the nonscientist, focusing on historical case studies. Until then, says Kuhn, "I'd never read an old document in science."
The experience convinced him of "what very very good science older scientists did," even when specific conclusions went against the modern grain. "It had stature as science and had to be taken seriously," he says, "which was very different from what I had expected."
His expectations had been molded by the conventional idea that there were two ways to answer a question--the right way and the wrong way. Thus the history of science had been seen as a "succession of individual, isolated discoveries, which, together, add up to the sum of scientific knowledge." The historian of science celebrated cases where someone seemed to have anticipated the current and "correct" answer to a question, and deplored or ignored cases where someone had let his vision be fogged by superstition and mumbo-jumbo.
Kuhn tried instead to follow a procedure advocated by Bertrand Russell in his "History of Western Philosophy." "In studying a philosopher," Russell wrote, "the right attitude is neither reverence nor contempt, but first a kind of hypothetical sympathy, until it is possible to know what it feels like to believe in his theories."
Along with this enhanced respect for the science of the past, a second perception became vital to Kuhn's later thinking. He found that it was "hard to see how, without all these earlier stages, we could have had what we ultimately got." In the third century B.C., the Greek astronomer Aristarchus theorized that the planets revolve about the sun, Kuhn points out, but organized science was unprepared for the idea and quite properly dismissed it. Great leaps forward, according to Kuhn, are rare events that occur only after prolonged periods of tradition-bound, imitative, "normal science." Science usually operates within a rigorous framework, and "frameworks must be lived with and explored before they can be broken."
So the typical scientist, as Kuhn came to perceive him, is far from the objective, free-thinking skeptic of textbook legend. He is, rather, someone who takes what he has been taught largely on faith and applies it to solving an inherited agenda of "puzzles," which Kuhn defines as "something that you ought to be able to do with existing theory if you're clever enough." What's more, this is an entirely commendable activity in Kuhn's scheme of things. "It takes great ability," he says. "It is not hack work." And it is as important to the growth of knowledge, he insists, as the trailblazing stuff that gets most of the attention.
In celebrating the role of the "normal scientist," Kuhn found himself at odds with British philosopher Karl Popper, then the preeminent man in the field, and then and now a formidable opponent. Popper did not deny the existence of Kuhn's "normal scientist," but dismissed him as "a person one ought to feel sorry for," "a victim of indoctrination," and "a danger to science and, indeed, to civilization."
Popper and Kuhn (and their respective disciples and allies) also became embroiled in a debate over the existence of absolute truth as the ultimate destination of scientific progress. Ironically, Popper had been a rebel among philosophers of science by challenging the logical positivist assumption that theories can be verified, and that verification is the hallmark of good science. Verification is impossible, Popper had argued. Theories can only be falsified, he said, and the sign of a good theory is that it seems, at least temporarily, to defy the most strenuous efforts to falsify it.
According to Kuhn, a theory can never truly be verified or falsified, but merely lived with--much as a person lives with a suit of clothes until it no longer seems to fit. And there is no magic moment when this happens, he says. Instead, a body of theory supports the basic "puzzle-solving" work of science for a time, and then, gradually, encounters more and more "anomalies"--puzzles that seem to defy solution. In the ensuing "crisis," new theories are propounded, but only when one of them captures a sufficient following in the field is the old theory abandoned--just as the old suit is abandoned only when a new one is at hand.
The concept of "normal science"--a communal activity guided by a group of shared models and assumptions--rang true with actual scientists, because, according to Michael Mahoney, a historian of science at Princeton, "this was the first description of their undertaking in which they really could recognize what they were doing." It caught on with nonscientists as well, because, in the words of historian David A. Hollinger of the University of Michigan, "so much of what Kuhn says about scientific communities seems to apply so strikingly to other kinds of communities . . . Historians are moved by Kuhn's sense of what a tradition is, what conditions sustain it, and what the relation is between tradition and innovation."
Kuhn was not the first person to challenge the idea of science as a relentless march toward truth, with each generation subjecting nature to the cold light of "the scientific method." And "Structure" was not the only book to suggest that scientists are humans too, with the full complement of human values and motives. Kuhn himself cites Norwood Hanson, Michael Polanyi, Paul Feyerabend, Stephen Toulmin, Imre Lakatos and Mary Hesse as rough contemporaries whose writings "look harder at actual scientific practice and point out the inadequacies of the logical empiricist tradition."
"There was something going on," he says. "People were beginning to take the history of science more seriously." But recognition is a whimsical business. People like to associate an individual with any major intellectual departure, and Kuhn, for better or worse, has become the individual associated with this one. Perhaps it is because he has expressed himself so forcefully and uncompromisingly, and even, according to his critics, ignored certain troublesome details from his own field, the history of science.
The criticism has homed in on Kuhn's claim that specific traditions tend to dominate science for long intervals, while innovation is reserved for special, and brief, occasions. This may be true of astronomy, says William Provine, a historian of science at Cornell, but "if you take something like the Darwinian revolution, I just don't find Kuhn's structure--the particular structure that he suggests--very illuminating. Darwin started a revolution in 1859, you could say, with 'On the Origin of Species.' But when does that revolution become normal science? You've got really a hundred years before the idea of natural selection really jells . . . then it comes together for perhaps two decades, and falls apart at the seams again."
One of the things that distinguishes the philosopher of science from the historian of science, as a rule, is an interest in how things ought to be as well as how they are. It is on this level that the Popperian view still enjoys its widest support and the Kuhnian enjoys its narrowest. Many have argued (as did Carl Sagan on his "Cosmos" TV series) that the modern scientist has become a plodding specialist, and ought to emulate the breadth and boldness of the ancient Greeks.
But Kuhn is doubtful. "I think there are terribly good historical reasons," he says, "for the increasing separation between philosophy and the technical sciences, and it's something that's been going on since the 17th century, when the two were very, very close together . . . There is just no prospect of returning and being Greek again or, for that matter, being 17th-century British or French again. It would be the end, probably, of both science and philosophy to try."
In times of crisis, scientists tend to behave more like philosophers, says Kuhn, citing Albert Einstein and Niels Bohr as notable 20th-century illustrations. But science would not fare better, in his opinion, if wide-ranging speculation and skepticism became standard. Every theory has its holes, and if scientists always focused on them, he believes, science could come to a standstill.
Because of his insistence on the virtue of conformity, Kuhn has been called an advocate of irrationality and even "mob psychology"--a charge that has left him "totally flabbergasted," he says. "I would have taken it for granted that what scientists are doing is behaving rationally, by and large. But I certainly am saying that rationality won't get you all the way there." Two basically rational people, he insists, can look at the same evidence and come to different conclusions, because there are no "laws of thought." Yet he admits he has been "too strident" on this point, for the same reason that, he says, he has exaggerated the unity of science. In both cases, he has been trying to "redress a balance."
When Kuhn left Princeton for M.I.T. three years ago, he moved from a department of history to a department of philosophy, and in keeping with that shift he has become more and more caught up in the nature of language--including the language of science and the language of specialized fields within science. In his next book, he intends to explore the role of language in the enforcement of scientific tradition, and the communications problems that arise when a scientist tries to argue with someone from a different tradition.
This is all very tentative, however, since Kuhn has not even begun writing yet. One thing is definite. The word "paradigm" will play a small role, if any, in the new book. "Not because the idea has been gotten rid of," he explains, "but because of what has happened to the word. I just can't use it anymore." But he will hold onto a treasured memento of "paradigm's" heyday--the original of a Kuhn-inspired New Yorker cartoon (bought from cartoonist Lee Lorenz), in which a woman congratulates a man she has met at a cocktail party for being "the first person I ever heard use 'paradigm' in real life."