July 26, 2023. Thomas Kuhn, 1922-1996, is inescapable. If you find yourself in a debate about “truth,” there is a good chance that some blowhard will invoke this philosopher’s ideas. Below is an updated version of a profile of Kuhn that I wrote for my book The End of Science. My hope is that this piece—which is based on three-hour conversation I had with Kuhn in 1991—will provide insights into this profoundly ambiguous, ambivalent thinker. –John Horgan

"Look," Thomas Kuhn says. The word is weighted with weariness, as if Kuhn is resigned to the likelihood that I will misinterpret him, but he is still going to try—no doubt in vain—to make his point. Kuhn utters the word often. "Look," he says again. He leans his gangly frame and long face forward, and his big lower lip, which ordinarily curls up amiably at the corners, sags. "For Christ's sake, if I had my choice of having written the book or not having written it, I would choose to have written it. But there have certainly been aspects involving considerable upset about the response to it."

"The book" is The Structure of Scientific Revolutions, which may be the most influential treatise ever written on how science does (or does not) proceed. It is notable for having spawned the trendy term paradigm. It also foments the now-trite idea that personalities and politics play a large role in science. The book's most disturbing argument is less obvious: scientists can never truly understand the "real world" or even each other.

Given this theme, one might think Kuhn would have expected his own message to be at least partially misunderstood. But when I talk to Kuhn in his cluttered office at MIT, he seems deeply pained by the breadth of misunderstanding of Structure. He is particularly upset by claims that he describes science as “irrational.” "If they had said a-rational I wouldn't have minded at all," he says with no trace of a smile.

Kuhn's fear of compounding the confusion over his work has made him press shy. In fact, when I first telephone him to ask for an interview, he turns me down. "Look. I think not," he says. After I finally talk him into meeting me, Kuhn expresses discomfort at the notion of delving into the roots of his work. "One is not one's own historian, let alone one's own psychoanalyst," he warns me.

He nonetheless traces his view of science to an epiphany that struck him in 1947, when he was working toward a doctorate in physics at Harvard. Reading Aristotle's Physics, Kuhn became astonished at how "wrong" it is. How could someone who wrote so brilliantly on other topics be so misguided when it came to physics?

Kuhn was pondering this mystery, staring out his dormitory window ("I can still see the vines and the shade two thirds of the way down"), when suddenly Aristotle "made sense." Kuhn realized that Aristotle invests basic concepts with meanings unlike those of modern physics. By motion, for example, Aristotle means not just change in position but change in general—the reddening of the sun as well as its descent toward the horizon. Aristotle's physics, understood on its own terms, is simply different from Newtonian physics, not inferior to it. So Kuhn decided.

Kuhn left physics for philosophy, and he struggled for 15 years to spell out the implications of his epiphany in Structure of Scientific Revolutions. The keystone of his model is the concept of a paradigm. Paradigm, pre-Kuhn, referred to an example that serves an educational purpose; amo, amas, amat, for instance, is a paradigm for teaching conjugations in Latin. Kuhn uses the term to refer to a set of procedures or ideas that instructs scientists, implicitly, what to believe and how to work. Most scientists never question the paradigm. They solve "puzzles," problems whose solutions reinforce and extend the scope of the paradigm rather than challenging it. Kuhn calls this "mopping up," or "normal science."

There are always anomalies, phenomena that that the paradigm cannot account for or that even contradict it. Anomalies are often ignored, but if they accumulate, they may trigger a revolution--also called a paradigm shift, although not originally by Kuhn--in which scientists abandon the old paradigm for a new one.

Kuhn holds that a revolution is destructive as well as creative. The proposer of a new paradigm stands on the shoulders of giants and bashes them over the head. He or she is often young or new to the field, that is, not fully indoctrinated. Most scientists yield to a new paradigm reluctantly. They often do not understand it, and they lack objective rules for judging it. Different paradigms have no common standard for comparison; they are "incommensurable," to use Kuhn's term.

Proponents of different paradigms can argue forever without resolving their differences, because they invest basic terms—motion, particle, space, time—with different meanings. The conversion of scientists is thus a subjective and political process. It may involve sudden, intuitive understanding—like that achieved by Kuhn as he pondered Aristotle. Yet scientists often adopt a paradigm simply because their peers do.

Kuhn rejects Karl Popper’s claim that science progresses when theories are disproved, or "falsified." Falsification, Kuhn contends, is no more possible than verification, because it wrongly implies the existence of absolute standards of evidence for judging theories.

Just because modern physics has spawned computers, nuclear weapons and other applications, Kuhn says, does not mean it is truer, in an absolute sense, than Aristotle's physics. A new paradigm may solve puzzles better than an old one, and it may yield more practical applications. "But you cannot simply describe the other science as false," Kuhn says. He denies that science approaches truth; science, like life on earth, does not evolve toward anything but only away from something.

Kuhn describes himself as a "post-Darwinian Kantian." Kant, too, believed that without some a priori paradigm the mind cannot impose order on sensory experience. But whereas Kant and Darwin each thought humans share more or less the same innate paradigm, Kuhn argues that our paradigms keep changing as our culture changes; whatever is universal in human experience, whatever transcends culture and history, is "ineffable," beyond the reach of language.

Language, Kuhn says, "is not a universal tool. It's not the case that you can say anything in one language that you can say in another." But isn't mathematics a kind of universal language? I ask. Not really, Kuhn replies, since it has no meaning; it consists of syntactical rules without any semantic content. "There are perfectly good reasons why mathematics can be considered a language, but there is a very good reason why it isn't."

By this point, I’m getting frustrated by Kuhn’s skepticism. Surely, I object, some scientific assertions are simply true or false. As an example, I bring up the claim of virologist Peter Duesberg that AIDS is not caused by the so-called human immunodeficiency virus, HIV. Duesberg is either right or wrong, I say, not just right or wrong within the context of a particular scientific-linguistic paradigm. Kuhn shakes his head and says:

“I think when this all comes out, you’ll say, ‘Boy, I see why [Duesberg] believed that, and he was onto something.’ I’m not going to tell you he was right, or he was wrong. We don’t believe any of that anymore. But neither do we believe anymore what these guys who said [HIV] was the cause believe.”

So are Kuhn’s own ideas true or not? "Look," Kuhn responds, frowning; he has heard this gotcha question before. "I think this way of talking and thinking that I am engaged in opens up a range of possibilities that can be investigated. But it, like any scientific construct, has to be evaluated simply for its utility—for what you can do with it."

Then Kuhn, having set forth his bleak view of the limits of science and indeed of all human discourse, proceeds to complain about the many ways in which his book has been misinterpreted, especially by admirers. "I've often said I'm much fonder of my critics than my fans."

He recalls students approaching him to say, "Oh, thank you Mr. Kuhn for telling us about paradigms. Now that we know about them, we can get rid of them." He insists that he does not believe science is entirely political, a reflection of the prevailing power structure. "In retrospect, I begin to see why this book fed into that, but boy, was it not meant to, and boy, does it not mean to."

His protests were in vain. In one seminar, he tried to explain that the concepts of truth and falsity are perfectly valid, and even necessary—within a paradigm. "The professor finally looked at me and said, 'Look, you don't know how radical this book is.'" To Kuhn’s horror, he became the patron saint of would-be scientific revolutionaries. "I get a lot of letters saying, 'I've just read your book, and it's transformed my life. I'm trying to start a revolution. Please help me,' and accompanied by a book-length manuscript."

He concedes he may be partly to blame for anti-science interpretations of Structure. After all, he compares scientists in the thrall of a paradigm to brainwashed characters in Orwell's 1984 and to drug addicts. But Kuhn emphasizes that he is pro-science, because science produces "the greatest and most original bursts of creativity" of any human enterprise.

Kuhn is also appalled that the term paradigm has become a staple of pseudo-intellectual discourse. As early as 1974, a New Yorker cartoon mocked the trend: a young woman gushes to a smug-looking man, "Dynamite, Mr. Gerston! You're the first person I ever heard use 'paradigm' in real life." The low point came in 1990, when the Bush administration introduced an economic plan called "the New Paradigm" (which was really just trickle-down economics).

Kuhn admits that Structure defines paradigm loosely. At one point paradigm refers to an archetypal experiment, such as Galileo's legendary (and probably apocryphal) dropping of objects from the Tower of Pisa. Elsewhere the term connotes "the entire constellation of beliefs" binding a scientific community together.

Kuhn denies that he defines paradigm in 21 different ways, as one critic claims. But he no longer tries to explain exactly what he really means by the term. "If you've got a bear by the tail, there comes a point at which you've got to let it go and stand back," he sighs.

I suspect that the ambiguity of Structure accounts, at least in part, for its power and persistence, its appeal to science skeptics and worshippers alike. Kuhn’s prose, like his speech, is never straightforward; he hedges all his statements with subjunctives and qualifiers. Structure should perhaps be viewed less as a work of philosophy than of literature, subject to multiple interpretations.

Here is my interpretation. Kuhn’s epiphany in his Harvard dorm room back in 1947 was a kind of mystical vision. Kuhn saw—he knew!—that reality transcends language; any attempt to describe it obscures as much as it illuminates. Yes, many mystics have said as much. I agree with Kuhn that no matter how far science progresses, it will never solve the mystery of existence.

But Kuhn takes this insight too far. He insists that because all theories fall short of absolute Truth, we can never call any of them “true”; because we cannot discover The Answer, the final solution to the riddle of reality, we cannot find any answers. This extreme skepticism is absurd. Science has given us many durable truths, embodied in theories such as heliocentrism, the atomic theory of matter, general relativity, the Big Bang, evolution by natural selection, DNA-based genetics, the germ theory of infectious disease.

Speaking of infectious disease, Kuhn’s prediction that Peter Duesberg would come to be seen as neither right nor wrong turned out to be wrong. Terribly wrong. The denial of the HIV/AIDS link is now viewed as morally as well as empirically wrong. In part because of Duesberg’s influence, the South African government withheld anti-retroviral medications from its citizens for years; that decision, according to one study, resulted in more than 330,000 avoidable deaths.

And yet, incredibly, a U.S. Presidential candidate, Robert F. Kennedy Jr., has revived Duesberg’s claim that the HIV/AIDS link remains unproven. Perhaps Kuhn was right after all when he said, in response to my insistence that some claims are either true or false, “We don’t believe any of that anymore.” Thomas Kuhn is the prophet of our post-truth era.

Further Reading:

See my profiles of philosophers of science Karl Popper and Paul Feyerabend.

If you doubt we live in a post-truth era, check out this New York Times profile of old spoon-bender Uri Geller. It does not matter, the Times implies, whether Geller actually bends spoons with “psychic powers” as opposed to sleight of hand; what matters is that Geller is entertaining. And then there is the UFO insanity…

Filmmaker Errol Morris, who briefly studied under Kuhn in the 1970s, ended up loathing the man and his philosophy. Morris’s savage criticism made me reconsider my view of Kuhn. See my conversation with Morris as well as these columns:

Did Thomas Kuhn Help Elect Donald Trump?

Second Thoughts: Did Thomas Kuhn Help Elect Donald Trump?

Filmmaker Errol Morris Clarifies Stance on Kuhn and Trump

Was Thomas Kuhn Evil?