Structural Realism, again

I fear I did not express myself as simply as I might have. My objection to Cao is that something must be ceded to Kuhn. One can of course try to oppose Kuhn’s thesis root and branch, but to do so one had better counter his concrete examples, or one had better present an equally persuasive and wide-ranging history, but to a di¤erent e¤ect. Perhaps Cao thinks his book provides just such an alternative, but alas, here a history of 20th century …eld theories simply doesn’t cut any ice: it is a history of normal science, in Kuhn’s terms, at least the way Cao tells it, devoting no time at all to the development of quantum physics, and hardly any to the discovery of special relativity, the two really revolutionary steps in physics in the last century. True, there remains one other plausible example of revolutionary science, and on this Cao does have something to say: the quantization of gravity. But this revolution is still in the making; one simply doesn’t know whether gravity will be accommodated along the lines Cao suggests; one just doesn’t know if his “gauge …eld program”, “geometric program”, and “quantum …eld program”will …nd a happy synthesis.1 My own suggestion is similar to Worrall’s, namely that at the microscopic level we give up on the more traditional, picturesque, common-sense idea of ontology the sort of story philosophers and historians …nd so easy to tell and embrace a more abstract, structural account of thing-hood and object-hood. But I add that we should also accept that the history of dynamics shows a very special character, very di¤erent from other branches of physics and other empirical disciplines. We should accept that dynamics is concerned with real structures to physical phenomena, but ones which recur in many di¤erent applications, embracing very di¤erent “ontologies”, in the traditional sense of the term. And since these dynamical phenomena are spread across quantum and classical, relativistic and non-relativistic regimes from particle physics to thermodynamics and condensed matter physics here we have a kind of continuity (structural continuity) across domains treated by theories that di¤er in radical, revolutionary ways. This is a kind of continuity wholly neglected by Kuhnians. Insofar as Cao considers this positive claim not much he objects that “it is not the question as to whether there is progress (...in an instrumental sense), or whether there is something in science that can be retained (.....empirical data...) in the development of science; but rather the question of whether there is cognitive progress....in the sense that we can have more and more true knowledge of what exists and happens in the world.” (1, p5-6). It is no objection as it