Incommensurability and Private Language

– David Bohm argues in his talk in ‘The Structure of Scientific Theories’ that terms in a given scientific theory only have meaning within the context given by that theory. This can probably be called ‘strong incommensurability’ – no two theories seem to be able to talk to each other.

– What this leaves us with is a kind of private language for science – private theory language. If the terms in a theory have their meaning only within the context of that theory, then it would seem that, as far as theories are concerned, scientists are unable to talk to each other. Given, however, the fact that scientists do talk to each other (and sometimes even about each others theories) there must be a snag somewhere.

– Bohm’s solution (and he later acknowledges that though it looks as if he’s advocating a kind of solipsism, he’s not) is to try and show that until a kind of common language can be adopted, confusions will continue to crop up in theory development. He cites a number of scientific cases from quantum mechanics where confusion abounds. Some familiar examples might be von Neumann, Kepler/Newton, etc.

– I think it’s fair to here identify Bohm to be paying tribute to the positivist tradition (Carnap et al) in his effort to move from ‘private theory language’  to a common kind of language – a project which saw a large reaction in 60’s and 70’s philosophy of science, especially in the area of theory-laden observation, which attacked the idea that there is in fact even neutral sensory data and neutral language to translate a theory from and into.

– Despite significant confusions in science (Bohm is correct to identify this) it seems a bit shaky to assert that this is both something to assert that this confusion is something to be avoided at all costs by adoption of a more neutral language (even though a Wittgensteinian picture of language may be of help here). Such confusions are only a strict problem if they stem only from theories not being able to talk to each other and do nothing to advance science – and quite often, these confusions help to sharpen, clarify and discard theories and concepts and so help science to advance forward.

– An example here that Bohm cites is malaria – which, throughout history, has had many different theories formed about its origin, structure, spreading, etc. Bohm notes that every different theory here is incommensurable – theorized causes ranged from bad air, damp air, etc, which all seemed to be confirmed by the data – and that effectively, each theory had nothing in common other than the fact that each dealt with malaria.

– In rebuttal, Robert Causey argues that far from demonstrating strong incommensurability, this merely shows that some theories are harder to falsify and some easy to confirm. The current (correct) theory of malaria makes sense of the same data as earlier, more primitive theories (damp air, bad water, etc) – Causey more or less argues that the history of malaria shows that, far from being incommensurable, these theories dealt with the same problem and the same data. Causey further argues that to show the kind of incommensurablity that Bohm is driving at, Bohm would have to show that (1) the problems dealt with by the different theories really were different problems with only the mere appearance of being the same (2) that the terms used by the different theories really were different and (3) that the differences in these terms and their meanings are different enough to show that the problems the theories were dealing with really were different problems.

– This, though a crude sketch, shows that incommensurability requires a fairly high burden of proof if it’s going to be asserted in as strong of a form that Bohm asserted.


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