"Representing Electrons" by Theodore Arabatzis

An ambitious and pretty successful biography of the electron

Theodore Arabatzis, Representing Electrons: A Biographical Approach to Theoretical Entities. Chicago and London: The University of Chicago Press, 2006

In Representing Electrons, Theodore Arabatzis gives a detailed account of scientific inquiry into the electron, covering roughly the years 1891-1824. The main message is that scientific entities have a "life of their own": they can act independently of theory, theoreticians, and experimenters. In delivering this message, Arabatzis makes a bold and largely successful attempt to bring the historical and philosophical approaches into a mutually stimulating relationship.

You can see Arabatzis’ dual interest in the history and philosophy in his choice of advisors and collaborators. While at Princeton University Arabatzis came into contact with the philosopher Bas van Fraassen, and numerous other philosophers are energetically deployed in the body of the book: Karl Popper, Larry Laudan and Thomas Nickels are quoted on the topic of “problem situations”, Paul Feyerabend and Ian Hacking on scientific realism, and Hilary Putman on theories of reference. Also featured in the author's acknowledgments are prominent historians of science, including Jed Buchwald, Warwick Taylor and Ernan McMullin.

In Representing Electrons, Arabatzis puts his multi-layered background to good use. Three themes dominate the book: realism and meaning change; the "discovery" of scientific entities; and the autonomy of theoretical entities. In Arabatzis's account, each of these themes has a historical and a philosophical dimension.

Take the topic of scientific discovery. Here, Arabatzis corrects the commonly-held view that J.J. Thomson “discovered” the electron. In doing so he uses the historian’s tools, probing scientists’ ideas through their scientific papers (such J.J. Thomson’s Cathode Ray article in Philosophical Magazine) and other writings (Lorentz’s Nobel Prize speech, for example. In later chapters he uses interviews conducted by Thomas Kuhn.) But this historical spade-work is guided by a philosophical discussion of “discovery” that draws on Hacking, Kuhn and Nickles. Here Arabatzis argues for the possibility of an account of discovery that is realism-neutral, and stresses the gradual, consensual nature of discovery: what we call “discoveries” are usually something more like “constructions.”

A similar pattern emerges in the next four chapters. Here, Arabatzis goes into considerable detail when dealing with the key episodes in the evolution of ideas about the electron, following the concept as it moves between various stages within physics (from classical to quantum and relativistic physics) and between disciplines (physics and chemistry). But his account is held together by the broad idea that the electron had a "life of its own," a capacity to throw up problems and suggest solutions.

Throughout the account, Arabatzis keeps a close eye on the stability of the "electron" concept through time and between practitioners. This conceptual stability comes to the fore in the concluding discussion about meaning change and realism in science. Arabatzis goes over some responses to Paul Feyerabend, who argued from meaning change to the non-existence of unobservable entities. When these responses fail, what is left for the realist? Arabatzis gives a two-fold answer. First, the case for realism can be supported by reference to the "writings" of the putative entity: if multiple observations give evidence of the same unobservable entity, you can be pretty sure the entity is real. Secondly, the case for realism can be supported by a historical account of a concepts' stability over time.

The final paragraph of the book draws out the implications of these arguments for historical accounts of the electron. Hence the attempted union of history and philosophy is carried right to the end of the book. Is this attempt successful? On the whole, the answer must be “yes.” There is a danger here of artificially gluing different disciplines together, but Arabatzis largely avoids this danger. The philosophical discussion in the concluding chapter draws on examples from the author’s historical account; during the historical discussion the reader is constantly reminded of the philosophical questions at hand; and the philosophy comments not only on the science of microphysics but also on the methodology of historians of physics.

One might complain that the philosophical discussion about realism and meaning change is independent of the “biographical approach” that Arabatzis takes to the electron. At least, Arabatzis seems to be in two minds about this. On the one hand, he pursues the “historicist” approach to discovery precisely because it does not require any prior commitment to realism or anti-realism: it keeps everyone happy. On the other hand, he writes the concluding chapter (on meaning-variance and realism) largely to justify his historical methodology: “for those who disbelieve in the existence of unobservable entities...a historical approach devoted to its representation may seem vacuous.”

In Arabatzis' defense, the final chapter does explore the implications of the historical account for the realism debate (not just the other way round). And his equivocation here may be just another sign that historians and philosophers (not just Arabatzis) have inconsistent aims. To a historian, who is worried about what happened in the past, the key criterion for existence of an entity is whether the entity was significant for past scientists. To a philosopher, the key criterion is whether it is, in fact, right to think that the entity exists. If Arabatzis is in two minds here, the problem does not lie with him, for being inconsistent, but with the two disciplines, for being different; Arabatzis' only real fault is not to clearly acknowledge this difference.

In the well-tilled field of historical research into the electron, novelty is crucial to a book’s success. The chief novelty in Representing Electrons is is the idea that concepts have a "life of their own." This idea does give rise to a fresh retelling of the atomic story: a vivid picture emerges of the electron standing on the outside of theory, teasing physicists into dead-ends and leading them on to unexpected new insights.

But Arabatzis has only given us a new picture insofar as he has applied it to a new entity: the ideas behind the picture are unexciting. For example, Arabatzis writes about Sommerfeld's selection rules, and how his “struggle to discipline the electron in a principled way ran into difficulties with its writings.” But do these metaphors convey anything more than the mundane fact that Sommerfeld had trouble matching his theory about the electron to his observations about it? A similar question may be asked about the fact that physicists found heuristic value of theories, and that they had trouble making the concept of the electron internally coherent. If the answers to these questions are “no”, this is not to say that there is no value in Arabatzis' biographical approach. It just means that the value lies in its contribution to the narrative structure of the book, and not to its philosophical depth.

One can always make quibbles about exposition, especially when an author tries to describe technical paths of reasoning. Overall Arabatzis does a good job here: a basic knowledge of maths is required to understand the derivations, but most of the discussion is within the reach of the ordinary reader. However, the book would benefit from more images of the relevant theories (eg. of atomic structure) and experimental results (especially spectral patterns). This would not just aid reader understanding. Copies of original diagrams of the electron would give a better idea of how physicists "represented" the electron to eachother and to themselves.

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Notes on ACAAPNZ 2008 II

A second highly selective selection from the 2008 conference of the NZ branch of the Australasian Association of Philosophy.

When not to have an Argument: the Different Explanatory Goals of Population Biology and Evo-Devo. Brett Calcott (ANU)

This talk was an attempt to resolve (in so far as it can be resolved) the debate between population biologists and evolutionary developmental biologists. A persuasive talk, but Calcott may have missed something important. I should note that part of Calcott's project is to unify evo-devo explanations with pop-bio explanations by showing how they both fit into a single account of explanation -- the “difference-maker” account of explanation. But the meat of the talk comes in Calcott's account of how explanations differ between the two approaches to biology.

Calcott distinguishes between “population-level” and “individual-level” explanations for evolutionary change. The former uses the genetic make-up of a population, plus the mathematical theory of genetic change, to explain changes in that genetic make-up. The latter uses certain physical differences between two stages in an individual's evolution, plus a knowledge of bioengineering, to explain certain other physical differences between the same two stages.

Calcott elaborates this distinction by saying that the former explanation is one of motive, and the other of means. Imagine an explanation of why a child got the chocolate bars on the top shelf in the kitchen. One could say that the child liked chocolate very much, so he was motivated to get it. Or one could say that he used a stool to help him reach the chocolate – he had the means. Both of these are genuine explanations of the child's behavior; whether we are satisfied with one or the other will depend on what we already know and what we want to find out. We can't ascribe motives to evolution, of course. But it seems reasonable to distinguish between what drives an evolutionary change (gene frequencies and their interactions) and what facilitates it (ie. how adaptive changes in structure to an individual are underwritten by other structural changes).

If this distinction holds, two things are clear. First, Calcott's distinction cuts across another popular distinction that is sometimes used to account for the disagreements between evo-devo and pop-bio – that between “proximate” and “distal” explanations. How can we explain, say, the human scab? We could give a biochemical account of why blood goes hard when exposed to air, and how this helps to heal the wound underneath. We need not look to the past to do this. Or we could try to explain how the tendency to form a scab has evolved – how it has come about that humans have the kind of biochemistry that leads to scabbing. This would certainly involves studying the past. Sometimes evo-devo is said to give “proximate” and pop-bio to give “ultimate” explanations.

Against this, Calcott insists that individual-level explanations, as he describes them, can account for how current phenotypical traits came about. After all, those explanations tell us how the structure of an individual at one point of time leads to a different structure in the same individual at another time. It tells us the mechanical means for this change. If we want a more fine-grained account of change over time, we just give a continuous series of these individual-level explanations.

As Calcott points out, certain “lineage diagrams” do just this. The lineage diagram we all know is of human evolution: a series of imags of our species in profile, running from the hunched and hairy ancestors to the pale and upright modern human. This doesn't explain much. But a more sophisticated diagram might. To illustrate, consider a set of instructions on how to make an oragami figure. These usually consist in a series of five or six drawings of different stages along the way to the final figure. And each drawing has dotted lines and arrows that tell you how to get to the next figure – what combination of small changes are needed in order to add a wing here, an envelope there, a sharp point there. Producing these “instruction series” is one job of biologists, and Calcott has all the right slides to show that they take the job seriously.

Calcott is clear that his distinction between individual-level and population-level explanations defuses the debate between evo-devo and pob-bio, rather than resolving it. He points out that the two forms of explanation he describes can come into conflict. That is, one form can give an explanation of a phenomenon that the other can refute. In any particular case of such a conflict, there can be a dispute about which account should hold more weight. But this is just as reconcilable as any other dispute in science between two competing explanations for a phenomenon. No two correct explanations of the two kinds could ever disagree over the facts of evolution. In this sense, they are “commensurable.” What should not be disputed is that both of them can give insight into how species have evolved.

Now, all of this strikes me as pretty well on the right track. But I'm not convinced that Calcott has covered all the areas of serious disagreement between evo-devos and pop-bios. As I understand them, evo-devos do in fact propose a new population-level process of evolution. The don't just give us, for each evolutionary event, an account of how certain structural changes are grounded in other structural changes. They give us an alternative view of how natural selection occurs. On the old view, genotypes fix phenotypes. And evolution occurs when a new and better genotype is randomly produced and outlasts the other ones. On the new view, genotypes have a very loose hold on phenotypes. Evolution occurs when the environment changes and phenotypes change in response to it, without any genotypical adjustments occuring. Genes only change further down the line. They help to ground the new phenotype, but the new phenotype arose earlier and independently, as an adaptive response to the environment. In a phrase, phenotypes lead genotypes, and not the other way around.

One can argue about whether this new picture is really new, or just a new angle on the old one. But it is a matter of sociological fact (I thought, perhaps wrongly), that the evo-devo picture was, and is, new enough in appearance to cause a big split between the evo-devos and the pop-bios. And this really does seem to be a split about the way in which evolution occurs, not about two different patterns of explanation that can be applied to evolution. Hence Calcott's distinction does not help to heal this particlar split, even if it can heal others.

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Notes on ACAAPNZ 2008

ACAAPNZ = annual conference of the New Zealand branch of the Australasian Association of Philosophy

Naturally, the Australasian Association of Philosophy has a New Zealand branch and (just as naturally) this branch has a regular conference that takes place in New Zealand. Oddly, though, the 2008 conference had a lot of Australians. But there's a natural explanation for this. The Australian National University can't find enough top Australian philosophers to fill their gaduate programs, and New Zealanders get first pick of the international scholarships at the ANU. Couple this with the fact that some top thinkers at ANU have dual careers in the big and small islands of the South Pacific, and you get quite a lot of inter-breeding. And when the man with the dual careers is Kim Sterelny, the scruffy luminary of cognitive evolution, you get quite a lot of Australian philosophers of biology at your New Zealand conference. This is all to the good, of course. But it means there's lots of philosophy of biology in the following notes on the conference, and not a whole lot else. So in here (in this and the following two posts) is my very selective list of conference talks, and some thoughts on them.


Presidential Address: On Turing on Intelligence as an Emotional Concept. Diane Proudfoot

A curious talk with drama, video, and a spiky question-time. The puzzle about the Turing Test is that Alan Turing's original version of the test seems needlessly complex. It consists in a jurer who asks questions of two hidden objects. One is a real person and the other is either a real person or a computer imitating a person. The jurer's task is to judge whether the second object is a real person or not. But it seems like one could just as well get rid of the first hidden object, and ask the jurer to judge whether it is a human or not.

Proudfoot thinks that the more complex test was better for Turing because he thought of mind as an “emotional” and not just an “intellectual” concept. Which is to say that whether we judge an object to be thinking or not depends on “our own state of mind and training”, which can vary between judges.

Proudfoot drew on three bodies of data, two sociological and one historical, to make her case. One is that humans are naturally credulous when interacting with computers. This can be nicely demonstrated by quirky videos of humans led into conversation with blocks of moving metal. Another is that humans guard their uniqueness jealously. We don't like being taken in by mere metal. At the annual Turing test Olympics, humans are more often mistaken for computers than the other way round. The historical fact is that Turing did indeed say that thinking is “emotional” in the way described above.

What to say about these bodies of data? The audience consensus seemed to be that they are interesting, but that it is not clear how they explain Turing's preference for the more complex test. Perhaps the idea is that the complex test brings out our jealousy to counteract our credulity. But how does the complex test accomplish this? And if mind really is an “emotional” concept, then the judgements we naturally make about the intelligence of machines should be our raw data about that intelligence, not fallible hunches.

To the second question, Proudfoot responds that according to Turing, our emotional response to a machine is only one component of the machine's intelligence, the other component being a fact about the machine itself. So Proudfoot would presumably claim that our credulity is not part of the subjective component, and is fallible. She did not give grounds for this claim -- even so, it can still form part of a how-possibly explanation for Turing's complex test.

The drama from the talk came from a mock-up of Alan Turing's 1952 broadcast on the BBC. Not all the original listeners liked the original broadcast. One listener said it sounded as if it had been “read from a prepared script, and badly.” Others were flatly opposed to the idea that machines could think. The mock-up got a receptive audience, though, not least because it shown the hidden dramatic talents of some professors of logic – talents great enough that noone could work out who they were.

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