At the Science Prom in your Underwear

July 2, 2006 § 17 Comments

Quantum Mechanics: Historical Contingency and the Copenhagen Hegemony by James Cushing is an aging (first published in 1994, hah!) but interesting read in the philosophy of science. It is a bit mathematically meaty for Joe Public I suppose, but many of the core concepts are I think accessible to everyman.

In a nutshell, there are two rival theories of quantum physics: the widely accepted Copenhagen theory and the marginally accepted Bohm theory. Here is the important bit, for my purposes: both theories match observation exactly. That is to say, both theories rest on identical formalisms, produce identically the same predicted experimental results, and match all existing experimental data identically. Think of the formalism as being kind of a computer program: give it some initial conditions and it will tell you what the results will be of an experiment. Copenhagen and Bohm rest on the same formalism, because for any input to the two theories you always get the same output.

But nevertheless they are radically different theories. In the Copenhagen theory, against Einstein’s objections, God does indeed play dice. In the Bohm theory God doesn’t play dice, but events can instantaneously affect other events a vast distance away. So the two theories share the same formalism – the same outer mathematical structure which is a way of making the theory formally correspond to the data of experiments – and yet they have very different interpretations, that is, understandings about how the world actually works. It isn’t that any theory at all can match the data – that is, can share the same formalism. Obviously many theories exist which do not match the data. But in quantum mechanics more than one mutually incompatible theory exist which match the data perfectly, and the reason one is taken to be true (Copenhagen) is a matter of historical contingency; it isn’t because Copenhagen comports with observation and Bohm doesn’t.

Now, all I am doing is telling you all of this, not substantiating it, telling you why it matters, or anything else. Cushing does a great job of all that in the book, and I can’t possibly reduce the whole book to a blog post. Those who believe that the formalism is the scientific theory and that the interpretation isn’t science are commended to the text.

But with all that stipulated it becomes interesting to shift our attention to biology.

Fundamentally the problem with arguments over the scientific status of darwinian evolution is that it has no unifying formalism (warning: evil PDF format). There isn’t anything we can do in biology where we provide the inputs to a formalism and the formalism tells us in a fully generalizable way how reality will behave.

Now it is not true that there are no formalisms in biology. Given a DNA sequence I can tell you in general what polypeptide chain will emerge from a ribosome as a product of translation, for example. But it is true that there is no single overarching formalism which connects all of biology together. Darwinian evolution represents itself as the overarching theory which unifies all of biology: but darwinian evolution isn’t a formalism, it is an interpretation. There is no formalism in biology which represents the data. Darwinism is just a story about the data, an interpretation of the data, and one that could match an infinite number of mutually incompatible data sets; darwinian evolution is not a formalism and does not rest on any particular formalism. We can’t create hypothetical inputs to the theory of darwinian evolution and determine what outputs would result.

And there is no more formally valid a priori reason to believe Earnst Mayr’s story than there is to believe the Discovery Institute’s. Intelligent Design may not be “science” if interpretations lacking a unifying formalism are not science, but if ID isn’t science then neither is neodarwinian evolution. Neither one contains a formalism capable of reconstructing the observed data. Both are interpretations (at least logically) consistent with observed data, though having poked around in proteins and DNA directly myself I find the darwinian story laugh-out-loud implausible.

But you have your choice. If interpretation without a formalism can be legitimately called science, then both darwinian evolution and intelligent design are science: rivals on a footing no less equal than the footing of Bohm versus Copenhagen. If not, then neither are science. I’m not hung up on what kind of knowledge we call science and what kind we don’t. I am hung up on being consistent about it, though.

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