Lost In Translation? Part I: What Is Incommensurability And Why Should I Care?

I have some family and friends who are well disposed towards CAM in general and homeopathy in particular.  I’ve noticed that discussions of the relationship between their views and science are fraught.  At times it’s because they don’t really understand the CAM ‘therapy’ or science; at other times it’s like we’re talking in different languages.

The latter can be thought of as incommensurability: the lack of common units of measure shared by concepts that we’d like to compare.  Apparantly, this idea reaches back in time to Pythagorean geometers who had the notion that any two lengths were measurable by multiples of some common unit, hence are “commensurable“. One of their number subsequently discovered that this is not so, legend has it that the discoverer of “incommensurable” quantities (irrational numbers) was killed by his fellows.  Incommensurability is only a little less controversial today!

The cry of “incommensurable” is often heard when CAM modalities are threatened with a fair test of their claims, it’s become a standard ‘defensive’ gambit.  How valid is this defence along with the common invocation of the work of philosophers like Kuhn?

I thought that it might be interesting to explore this idea in the context of my on-going investigation of Thomas Kuhn’s “The Structure of Scientific Revolutions” (SSR, 1996).  To try and keep the discussion manageable, I’m going to present it in two parts.  In this instalment I’ll try to illustrate the abuse of the concept.  In the second, I’ll explore what Kuhn really said and tease out some (hopefully) useful lessons.

So, why bother spending time thinking about an academic concept from the philosophy of science?  The short answer alluded to above, is that people are using it in an attempt to exempt their favoured therapies (and even social policies) from proper scrutiny: it’s become a post-modern excuse.

Let’s just review a few of the many examples where the incommensurability gambit is deployed.  For instance, commenting on the implications of Evidence Based Medicine (EBM) for Traditional Chinese Medicine (TCM), Wainwright Churchill (136kb pdf) offers up the common CAM version of incommensurability:

“Chinese medicine does offer an explanation of how acupuncture works, but this is within a separate and incommensurable paradigm from the biomedical [ …] Many scientists believe that the scientific paradigm has absolute truth value, but philosophers such as Thomas Kuhn reject this. If no paradigm does have absolute value, there is no absolute basis with which to judge another paradigm. Any paradigm will appear limited or incorrect from the perspective of a different paradigm, so Chinese medicine will seem incorrect from a biomedical point of view, and vice versa

[…] different paradigms are incommensurable, meaning that their frames of reference are different so that the world depicted in one paradigm cannot be translated into another, just as not everything that can be said in one language can be said in another.”

“[…] Because of the incommensurability of paradigms, any CAM practised its original way cannot be the same as its biomedical version – they must remain two separate worlds. If the biomedical paradigm is adopted, the system will have the characteristics of that paradigm – materialistic, mechanistic, reductionist, linear-causal, and deterministic (many of the characteristics that inspire people to use complementary medical therapies). Biomedical research into that discipline will reflect the biomedical worldview. Statements such as ‘Yin and Yang do not exist’ will follow as unavoidably as night follows day.”

Is he right to state that Kuhn’s incommensurability thesis means that their can be no translation between ‘paradigms’?  Are there really no ways to compare TCM interventions with proper medicine?

(It should be noted that this quote demonstrates a fatal inconsistency: Churchill states that the world described by one paradigm cannot be translated into another: “just as not everything that can be said in one language can be said in another”.  Here he mistakenly equates complete incommensurability with partial translation.)

Sometimes I wonder whether incommensurability is just used to obscure the wishful thinking present in CAM ‘therapies’.  For instance, Coulter and Willis invoke incommensurability rather than the downright crankiness present in homeopathy as the reason for its incompatibility with modern medicine.

“In sociological terms, the issue is one of commensurability of paradigms. To argue for complementarity or integrativeness implies that the knowledge bases of the paradigms are commensurable – that is, they are not logically inconsistent. For example, in the paradigm that we now call conventional scientific medicine, dilution of a therapeutic substance weakens its potency. However, in the homoeopathic paradigm, dilution – even multiple times so that few molecules of the original substance remain – actually increases its potency. Presumably dilution can’t do both. The paradigms are incommensurable, and so the possibilities for combining treatments based on the two paradigms must be limited.“

On other occasions incommensurability seems to be used as a fig leaf to cover the embarrassingly primitive nature of CAM beliefs.  Take this extract from a discussion of the merits of Kampo (a Japanese version of Chinese herbal medicine):

“I would like to point out one of the biggest of such obstacles before I describe the details of Kampo medicine. Stated in a way that may astonish Western readers, with Kampo it is simply impossible to design a clinical trial which asks the question ‘is such-and-such Kampo prescription effective or not for chronic hepatitis?’ Out of ignorance, this approach has sometimes been taken in the West for the testing of Chinese herbal medicines, and one of the main themes of this lecture series is to persuade the readers that this kind of approach is not appropriate. As the readers may anticipate, the reason is the incommensurability of paradigms. The concept of chronic hepatitis simply does not exist in the Kampo paradigm.”

Is it really so that Kampo cannot be tested in a scientific (fair) trial?  Does this mean that chronic hepatitis is just called something else in the ‘Kampo paradigm’?  If not, shouldn’t this incompleteness be taken as an indication of the inferiority of this ‘paradigm’?

Hepatitis is an inflammation of the liver and can be caused by viruses, toxic agents and auto-immune disorders; are these agents really controlled by our beliefs?  If adherents of the Kampo paradigm were injected with the hepatitis B virus (HBV), for example, would they be immune?  How come infection rates for hepatitis B are up to 15% in South East Asia and China where Kampo (or Chinese herbal medicine) has at least some influence, but less than 1% in the non-Kampo UK?  Taking Japan, the home of Kampo, according to the CDC (quoted in this report (1430kb pdf) ) it has an intermediate rate of HBV infection (2-8%), whilst the UK’s is rated low (<2%): clearly no correlation between not having the infection as part of a ‘paradigm’ and not having the infection!

(Please note that I’m not refering to a necessarily general view of Kampo here.  I’m just discussing this author’s use of the incommensurability gambit.)

To subordinate the facts to a philosophical stance is clearly perverse.

It’s when incommensurability is used (267kb pdf) as a Trojan horse for introducing an ‘anything goes‘ relativism into state funded healthcare that the dangers become most obvious. (My thanks to the Freeborn John blog for the reference, contained in a fascinating discussion of the perversion of the word qualitative by some social ‘scientists’.)

What is striking about the plea of incommensurability is that it is frequently used to justify the existence of a barrier than cannot be crossed:  science can’t prove my ideas to be wrong (or even judge them) because they are part of an incommensurable paradigm.

This total barrier to communication and comparison is clearly self-refuting: if I can’t compare your theory with mine and decide which is best; how come you can reject mine?  Or, if our ‘paradigms’ are truly incommensurable how can you tell me exactly what it is that I ‘cannot’ understand?

This type of incommensurability also seems, at times, to be defined as one-way: science cannot evaluate my views as they are part of an incommensurable paradigm, but they are nevertheless right!  Here is a particularly outrageous example, courtesy of a homeopath who inhabits the halls of quackademe.

This is clearly a vacuous attempt to avoid the self-refuting nature of complete incommensurability: who gets to decide which way the one-way traffic flows?  Why can’t it be one-sided in favour of science rather than CAM, for example?  This ends up as nothing more than a partisan incommensurability.

So if the CAM version of incommensurability is so empty, did a man as bright and accomplished as Thomas Kuhn really advocate it?  If not, what was he really trying to get at?  When allegedly Kuhnian incommensurability is invoked – or disparaged – what are some useful points to bear in mind?

Those questions will be explored in part II.