Tuesday, 7 August 2018

The Structure of Scientific Revolutions

That inevitable moment in the life of every pretentious pseudo-intellectual has arrived: I have read Thomas Kuhn’s Structure of Scientific Revolutions, and now I will pontificate about it.

If you have no idea what I am talking about, the blurb tells us that Structure, first published in 1962, was “a landmark event in the history and philosophy of science”. The Introductory Essay in my copy opens: “Great books are rare. This is one. Read it and you will see.” You need more? Structure was the source of the term “paradigm shift”, and is a hell of a lot shorter than the source of the term “Catch 22”. (Admittedly less funny.)

Some preliminaries. I read the book once in 2015, prompted by those it has influenced. From the fans, the sociologist Harry Collins, and from the ranks of the detractors, filmmaker Errol Morris. In particular, Morris wrote a series of New York Times articles about Kuhn, starting with an episode from his time as Kuhn’s graduate student, when Kuhn ended an argument by throwing an ashtray at him. Now Morris has expanded his essays into a book. It is called “The Ashtray”. In preparation for reading it, I decided to read Structure one more time.

(I had an email exchange with Harry Collins about the Morris articles. In the last email Collins concluded that Morris was just out to make a buck on Kuhn’s memory. The email ended, “Hand me the ashtray”. Who ever said philosophy was dry and boring?)

The more important preliminary is that I am not, of course, a historian of science, a sociologist of science, or a philosopher. I know nothing of the book’s ancestors (I cannot comment with a shred of authority on who influenced Kuhn, or how original his ideas were), or its descendants (what influence the book had, what has become of its ideas, or the current critical view of it). I bought it, I read it twice, and here are my thoughts.

I. Scientists, Get Some Structure In Your Life. 

The early sections were revelatory. Kuhn provides his take on how science operates, and my reaction was a repeated stream of, “Yes, yes, that’s exactly how it is!”, punctuated by, “Why has no-one told me this before?” Kuhn explains that most of the time scientists have a collected set of opinions, theories, and methods, which is what he calls a paradigm. Within those theories there is a set of legitimate problems to work on. Working on them uncovers more facts to flesh out the details of the theory, or to refine or expand the theory. Kuhn calls this “normal science”, and he characterises it principally as “puzzle-solving”.

Some scientists may be affronted to have their life’s work likened to a child putting together a jigsaw puzzle, but it sounds spot on to me. It also explains why so many scientists seem strangely disinterested in the mysteries of nature that lie only a few steps beneath their work: the motivation, the challenge, the goal, is not necessarily to explain anything, but to solve a puzzle. That is not all scientists, and certainly not the most visible scientists, who honk on continuously about the deep secrets of the universe (to great public cheering), but it is the bulk of the worker bees, who buzz along from one tricky puzzle to the next.

The message this worker bee took from Kuhn, and the bit that had me wondering why no-one had explained it to me before, is that this is good. There is a romantic notion that “real scientists” invent new theories and make breakthroughs, and everyone else is a second-rate hack, a mere wannabe. Bollocks. Science is about filling in the details of our current understanding of nature. That requires skill, dedication, patience, tenacity, and creativity, and if you are a scientist, it is work you can be deeply proud of. If you have a nagging feeling that ultimately you are a failure until someone names a theory after you, then you need to pick up a copy of Structure.

My own field is a perfect example. In 2015 (a few months after I first read Structure) gravitational waves were detected in the LIGO interferometers. The result was announced to huge fanfare as a “breakthrough”, a “discovery”, and even heralded by some as a “revolution”. It was indeed an incredible scientific result, but it was 100% puzzle-solving Normal Science. A prediction from Einstein’s general theory of relativity was measured. It took 100 years; it took many decades just to work out what the theory predicted, let alone measure it. Some of my colleagues who cling to their childhood conception that real science means revolutionary discoveries, will argue that these observations also tested Einstein’s theory, to identify where it fails. Whatever spins your wheels, guys. So far all of the theory “testing” could just as well be called “validation”. For all we know, it will still be validation when these guys breathe their last disappointed breath. But they should not be disappointed. Comparing refined measurements against a theory, and filling in yet more details, is noble and essential work. Cheer up!

At this point you are probably wondering when I am going to get on to the juicy stuff with the revolutions and the paradigm shifts. If so, calm down, and read again from the start. If you are a scientist, your career is almost guaranteed to begin and end with the Normal Science, so get used to it. Plus, there was another revelation from the Normal Science sections.

The existence of a shared set of theories and opinions (i.e., a shared paradigm) is the true engine of scientific progress. This is what defines a science. The point Structure makes is that the alternative is a series of competing schools of thought — as in history, philosophy, economics, religion, etc., etc. What makes a science different is that there is enough evidence to lock everyone into just one agreed picture of what is going on. More precise data or new observations might lead to a new picture, but most of the time the situation is stable, and that stability is essential. A broad consensus exists for long enough to allow scientists to define a set of problems to solve, and to develop ever more sophisticated apparatus to perform experiments. Scientists often forget how important and how powerful that is. Without the consensus picture, without the paradigm, everyone is searching blindly, arguing over definitions and methods and making very slow progress. You cannot expect to win millions of dollars in funding for telescopes, particle accelerators and huge laboratory complexes, if no-one can agree on what fire is.

Put another way: the romantic picture of science as lone searchers who cook up brilliant new theories is exactly what science is not. A discipline filled with these glorious characters might be very exciting, but it is not a mature scientific discipline, and may not become one for a very long time indeed. Until it does, progress will be slow, and more likely nonexistent. (Yes, there is fun to be had applying this criteria to all the “scientific” fields we hate. Knock yourself out.)

So far, so good. But what happens when the current theory stops working? When inconsistencies show up, or data that does not fit? At first, nothing: usually the current picture can be modified to fit the new evidence, or the evidence turns out to be wrong; either way, the problem is likely to go away. But sometimes the problems mount up, and the current picture starts to break down. There is a crisis. Normal science ends, and there is a period much like the pre-science chaos: lots of ideas, which get increasingly desperate. People are in confusion, and some scientists may start to doubt their vocation: “nothing makes sense any more!” Finally there is a new idea, which does fit all the facts, or at least fits them better than before. People may resist it, but if it ends the nightmare of utter confusion, they will eventually settle on it. That becomes the new picture: the paradigm has shifted. If the new picture sticks, then eventually everyone calms down, and Normal Science resumes. Think the Copernican picture of the Earth orbiting the sun, the dawn of quantum mechanics, and Einstein’s theories of relativity. (Kuhn has many examples from chemistry as well.)

Once again, this rings true, and is much more compelling than the notion that a theory is “falsified” and then rejected until someone comes up with a new theory. Rather, a theory clings on for dear life, until it has no choice but to give in to its successor.

I have no idea if anyone ever really believed the “falsifying” thing. Falsifiability is associated with Karl Popper, but how many scientists have read Popper? Or Kuhn, for that matter? Our conception of what science is, and how it works, is so crude that it may as well have been explained to us in a child’s picture book. It probably was explained in a child’s picture book! “Structure” is good on this as well: scientists do not read scientific history, and that is also fine. The consensus of a shared paradigm means that there is nothing to be gained by reading old science, and in fact it may be worse than a waste of time. Newton’s ideas have been refined and are better presented in an undergraduate textbook than in Newton’s own writings. No-one reads Newton, or Maxwell, or Planck. Studying Einstein’s papers is not going to provide a deep insight into the great man’s thinking: in fact, Einstein’s personal thinking is far less useful than the collective wisdom of all those who have worked since, as condensed into text books and current papers. It is not surprising that Kuhn exudes a whiff of disgust at this — he studied the history of science through close reading of original texts — but the point is valuable: this is another of the defining features of a mature science, and another reason why it works so well. If there is an upheaval in your field when someone uncovers a genius’s long-lost manuscript, then your field is probably not a science.

All right. That’s the good stuff. The Normal Science, the sharp insights into what defines science, the passage through crisis and revolution. We are fine all the way up to the end of Section IX. Then it gets screwy.

II. Beneath A Collapsing Structure.

Kuhn talks about revolutions as a change in world view: scientists now see the world differently. Ok. Fine. We have a new point of view. But this is not strong enough for Kuhn. He struggles to impress on us just how fundamental this change is, almost, but not quite, claiming that the world itself changes. As Kuhn got excited about gestalt shifts (is it a drawing of an old lady, or a young girl?), and the nature of human perception, I became confused over just what kind of book this is.  Is it history — describing what has happened in the past, and identifying patterns in the history of science? Or is it amateur cognitive psychology — explaining how the human mind interacts with the real world and builds up (and changes) its interpretation of it? Or is it sociology — how communities of scientists operate? Or, finally, is it philosophy — a thesis about the very nature of reality and our (in)ability to know it? The book’s fans may claim that it is such a work of genius that it is all of these combined; its detractors as a failed mishmash.

Kuhn repeatedly frames the book as tentative, a “sketch”, an essay, to later be fleshed out into a full book. (Kuhn lived another 34 years, and never wrote that book.) If we take it in that spirit, we can almost overlook the oddities of the last sections. As the insightful signals start to sink into philosophical noise, there are still gems to be had. Even the troublesome notion of incommensurability, that scientists from two paradigms work in different worlds and cannot communicate between them, which is the starting point for the complaints Errol Morris makes — even this is a useful insight. It can indeed be incredibly difficult to communicate with those who see the world through a different framework. The history of science is packed with examples of old codgers who could not accept a new theory. Poincare and Lorentz, who got so close to the revelation of relativity, refused to ever accept it. Possibly they could not accept it precisely because their ideas were close to it. Possibly they were just stubborn. Like Planck (almost) said, science advances one funeral at a time. But this is not true of everyone: people do come to understand new theories, they do work out how to translate between them, and they do come to see the advantage of changing their mind.

In the last section Kuhn asks how science has made so much progress. His answer? Scientists are only human: whatever they have done, they will look back and call it progress. He brings up the standard claim that science approaches truth, and dismisses it as naive: the assortment of impressions we have collected during our haphazard intellectual journey can hardly be called truth. This makes it sound like Kuhn is doing a hatchet job on science, but how can he be, when his knowledge of science history and his appreciation of scientists’ achievements is, from page to page, deep and indisputable? When I got to the end of the book I read the last four sections one more time, and simply could not fathom his conclusions, or entirely clarify what they were.

Why does he say so little about the role of experimental data in both challenging paradigms and in resolving revolutions? In particular, why so little appreciation of the incredible improvement in the range and precision of experiments over the decades and centuries? In the Postscript, written several years later, he refers to the “progress” from Aristotle to Newton to Einstein and notes, “…in some important respects, though by no means all, Einstein’s general theory of relativity is closer to Aristotle’s than either of them is to Newton’s.” Whaaat!? He objects to the modern conclusion that Aristotle’s views were merely mistaken. Sure, Aristotle was very clever, perhaps he was the cleverest human who ever lived — why not? — but how could he be anything other than mistaken without a telescope to see the heavens; without a wristwatch, a precision balance or a micrometer to measure time, weight, and distance; without a pipette, a photographic plate, or a particle accelerator? Jeez, the man didn’t even have a bunsen burner! Of course he was mistaken! Ok, I get the point — the role of human misinterpretation, personalities and peer pressure have been overlooked and under-appreciated in the history of science — but reading Structure, I had a queasy sense of the scales being tilted so far the other way as to topple over entirely.

I take the point that data have to be interpreted, and Structure is good on how the same data may tell us different things before and after a revolution, and in between scientists will argue over what the data are saying, not to mention which data are relevant and correct, and which are irrelevant and flawed. The community may also settle on a conclusion before the data warrant it. (A wonderful set of cautionary examples can be found in The Golem.) That is the short-term picture, and it is invaluable to understanding how scientists operate, as communities of human beings, but it is not enough to explain the long-term success of science. With more refined study, a wrong answer will be found out, whether it takes a year, a decade, or a century.

Paradigms do not hit a crisis for social reasons. We would love nothing more than for the Earth to be at the centre of the universe, for there to be no universal speed limit, and for the intuitions we have built up about the world around us to apply at atomic scales as well. We cannot cling to those ideas, not because society does not allow us, but because they are wrong — demonstrably wrong. Surely this is a fundamental defining feature of science? Human beings love to be right, they love to persuade others they are right, and they love to delude themselves. In art, politics and religion you can win by force and by wit, and unfortunately those will get you a long way in science as well, but eventually you hit the hard wall of reality. Reality is the constraint that makes all the difference.

I am not the first scientist to read this book and wonder why he takes a stance on scientific progress so extreme as to seem deliberately obtuse. To step back from the long arc of the human study of nature, through gravitation, electricity, magnetism, atomic structure, molecules, DNA, the big bang, all of it, and to paint scientific progress as akin to communal back-patting, strikes me as truly perverse. He might argue that that is not what he meant, but if he meant something else, perhaps he could have been a little clearer about it?

Lurking behind all of this is a big question: what is science? Is it a Method, a procedure, a technique that humanity has hit upon, like cuneiform writing, Iambic pentameter, or the headlock? Or is it just another of those complex and pedantic cultural rituals, like Kabuki theatre, Catholic Mass, or cricket? Or is it the inevitable means by which an intelligent species can discover the nature of reality, through a powerful feedback loop of observation, analysis and identification of patterns? The first option is the schoolbook fairy tale. The second is the messy but fascinating world of scientific communities, which are well worth studying, and the proper subject of Structure. The third, which I am of course fond of, is nonetheless a wishful philosophical stance, and a waste of words to debate. I would argue, though, that there is scant evidence in all of human history and experience to make us seriously question it, and it is entirely compatible with the second option. It seems Kuhn thought differently, and his book left itself wide open to be embraced by the anti-authoritarian, anti-technology counter-culture of the sixties, and worse since.

That is a pity. It is a pity for him, because the very real achievements of his book have been obscured by the nonsense bred from its last sections. Most importantly, though, it is a pity for the rest of us, who have to live in a world that mistrusts science. Is it really all Kuhn’s fault? I do not know, but I do know someone who believes that it is. So now it is time to spend a few hours in a room with Errol Morris’s Ashtray.

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