Wednesday, February 8, 2012

Books: Kuhn vs Popper

Continuing my attempt to write something about every book I read. Even though this book's fairly short, this post goes on a bit as I try to get to grips with the most important parts.

The dramatic subtitle of Kuhn vs Popper by Steve Fuller is: The struggle for the soul of science. I don't know much about Thomas Kuhn or Karl Popper. What I was expecting from this book was a brief and accessible introduction to debates about the scientific method, using the tension between the two as a hook. What it actually turns out to be is a bit of a hatchet job on Thomas Kuhn. For example, one chapter explains why Heidegger cannot escape some responsibility for Nazism. The next asks "Is Kuhn the American Heidegger?" Leaving you thinking, "did Fuller just call Kuhn a Nazi?" Probably the book is best read by someone with a basic grounding in the subject already, something I don't have, but it was still clear enough to be worth reading.

Roughly speaking, Popper and Kuhn's approaches are as follows. For Popper, to decide between rival theories, scientists must set a test. Each theory makes a claim, and whichever is falsified fails the test should be discarded, regardless of its longevity or authority. (If your claim is unfalsifiable, it's not scientific.) Popper's vision is one of constant challenge for scientific theories, and regular failure, but scientists themselves have to be protected from the consequences of being wrong.

For Kuhn, scientists work within "paradigms". "Normal science" is an incremental advance. It increases the power of a paradigm but also brings up problems. When the collection of problems gets too great, a successful new paradigm emerges and a scientific revolution occurs. Most famous scientists engaged in "revolutionary science" rather than (boring) "normal science".

A paradigm is a sort of worldview. Here we run into some problems. Kuhn has been criticised for not having a clear definition of "paradigm" and using the term in different ways. What is probably the key feature of paradigms is that they are "incommensurable". "Incommensurability" is an even more problematic term. Incommensurable theories are radically different, like newtonian vs relativistic vs quantum physics. They are very different ways of looking at and describing the world. You will not understand newtonian physics if you assume that all particles are also waves, with indeterminate position and momentum.

What I think is the key to incommensurability is that it is impossible to clearly judge between two theories (at least, initially). There is such a gap between them that it is impossible to translate a claim made by one theory into terms that can be used to verify the other. In addition, while the new theory solves problems of the old, according to Kuhn, some information is always lost. Naturally, there will be also be things the new theory can explain, but has not yet explained. Faced with this situation, there can be no conventionally "scientific" contest between the two theories. I think Kuhn would go as far as saying that even in retrospect it is impossible to scientifically judge between paradigms. They can only be understood and validated in their own terms, which by definition(?) invalidate other paradigms. Instead there is a fracture in the scientific community, which is not entirely healed until supporters of the losing theory 'die off'. (Einstein never really reconciled himself to quantum mechanics.)

Whether this is really true is open for debate. Late last year, Errol Morris wrote a series of blog posts titled "The Ashtray Argument" in which he attacks the concept of incommensurability. In an interview, Kuhn claimed that incommensurability was "easy" - he got it from mathematics and used it as a metaphor. In maths, incommensurability refers to the fact that irrational numbers cannot be expressed as rational numbers of fractions. Pi as a fraction would be infinitely long. Supposedly, the guy who revealed the existence of irrational numbers was killed by the Pythagoreans for threatening their mystical worldview. They could not make the conceptual change from a world of rational numbers to one where some fundamental numbers were irrational. However as Morris points out: 1) this almost certainly never happened; 2) irrational numbers arguably supported the Pythagorean view; and most importantly 3) it wasn't the case that the Pythagoreans couldn't understand or judge the validity of incommensurability. Kuhn's founding metaphor appears to undermine his own theory.

Anyway, to round this off, when a new paradigm takes over, scientists rewrite history and make it look like science was always heading their way, in its inevitable march towards truth.

There is certainly a valid attack on the 'whig' interpretation of scientific history here - the view that science is always advancing and improving, in a fairly straight line. However it has a number of negative effects. One is to break science into a multiplicity of specialised paradigms. These are insulated from criticism from outside, both of their correctness and their value. In fact, Fuller argues, it served the Cold War military-industrial complex. It persuaded scientists to work on incremental improvements within the constraints of a paradigm ("normal science") rather than to think freely. It protected scientists from criticism of their political and military role - and from thinking about it for themselves.

Popper was initially linked with the Frankfurt School and critical theory. However while he kept a lot in common with them, he also disagreed on some major points. In particular, his political programme was more provisional, experimental and (arguably) democratic, compared with the Frankfurt School who launched something like a(n unsuccessful) propaganda war against capitalism. Popper was much more engaged with politics and his critics than Kuhn, and it may be that his reputation suffered as a result. In contrast, Kuhn wrote no significant books other than The Structure of Scientific Revolutions and answered criticisms only very erratically. This ties in with Morris' picture of Kuhn as someone who forbade him from attending rival lectures and threw an ashtray at him when he challenged incommensurability. (Though Morris' story has been challenged, most notably by Thomas Kuhn's daughter.)

All this might seem a largely irrelevant argument, while science continues successfully on its way. In fact, one of the chapters is titled 'Why philosophers get no respect from scientists'. It's not easy to summarise - I'm not sure it's entirely clear - but part of the reason is that science tends to relegate failed thinkers to "philosophy" while adopting successful ones as "scientists" (eg. Newton vs Descartes). Most scientists working within their specialised niche see no value in thinking more broadly. If they do conduct such "philosophical" speculation it tends to be after they have had their great scientific successes and have entered a "fallow" period.

The Kuhnian position actually relegates philosophers to "underlabourers" working at fringe problems to support scientists. It is quite explicitly uncritical. In fact, it calls for both a non-judgemental history from the perspective of the subjects, and a heroic history aimed at inspiring contemporary scientists. By contrast, a Popperian history of science builds normative assumptions into its story, highlighting how science has deviated from them.

The importance of this is twofold. First, in judging what is good and bad science epistemologically. For example, Popper and his followers had issues with evolutionary science and its ability to claim any change as making an organism "fitter". Evolutionary biology is probably in a better state today, but it has spawned the very dubious field of evolutionary psychology. The movement of physics away from experimentation and observation and into ever more abstract mathematics is another case where scientists methods need to be questioned. I wonder whether this relegation of philosophy has actually encouraged the growth of pseudo-science and non-science. It makes people (both specialists and not) unfamiliar with criticising methodologies. It also looks like science it is itself shielded from criticism, making it appear one among a range of belief systems which cannot be criticised or compared.

Secondly, the philosophy of science is required to make ethical judgements. Some would pretend that science is simply an amoral search for knowledge, but this is clearly not true. Think for example about a virologist choosing whether to research a cure for HIV or to research new biological weapons. In the 20th century scientists were involved in some great ethical questions, most notably the development of nuclear weapons. The fact that the ethics of this project were and are still not clear does not mean scientists can evade responsibility. It might appear that much contemporary science is far removed from ethical questions, but the example of German scientists is instructive - in 1914 they swung behind Germany, including shifting focus from physics to "the epistemologically inferior" chemistry. (The great exception was, of course, Einstein.)

One thing about this book is that I came out feeling I had a much better understanding of Kuhn's philosophy than Popper's. It did leave me wanting to find out more about Popper, but his own works seem quite daunting. I'll have to look out for an introduction.

"How can a mere philosopher devise criteria distinguishing between good and bad science, knowing it is an inutterable mystic secret of the Royal Society?" - Imre Lakatos (1973)

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