Alberto Cordero

Using the optical ether as a case study, this article advances four lines of consideration to show why synchronic versions of the divide et impera strategy of scientific realism are unlikely to work. The considerations draw from the nineteenth-century theories of light, the rise of surprising implication as an epistemic value from the time of Fresnel on, assessments of the ether in end-of-century reports around 1900, and the roots of ether theorizing in now superseded metaphysical assumptions. The typicality of the case and its impact on diachronic versions of the strategy are briefly discussed.

Breaking away from logical-empiricism, in the early 1950s Stephen Toulmin presented empirical theories as maps, thereby opening a fertile line of reflection about background interests and their impact on abstraction in scientific theorizing. A few years later, pointing to the “qualitative infinity of nature,” David Bohm denounced what he regarded as counterproductive constraints on the scientific imagination. In realist circles, these two strands of suggestions would be variously supplemented over the following decades with further recognitions of the epistemic merits of partial approximate descriptions and the role of background knowledge and interests in scientific theorizing. Rompiendo con el empirismo lógico, en la década de 1950 Stephen Toulmin presenta como mapas las teorías empíricas, abriendo así una línea fértil de reflexión sobre los intereses que motivan cada teoría y el impacto de dichos intereses en la abstracción en la teorización teórico/científica. Unos años más tarde David Bohm, señalando el “infinito cualitativo de la naturaleza”, denunció lo que él consideraba restricciones contraproducentes en la imaginación científica. En los círculos realistas, estas dos visiones serán complementadas de diversas maneras durante las siguientes décadas con reconocimientos de los méritos epistémicos de las descripciones aproximadas parciales y el papel de los intereses y conocimientos previos en la teorización científica.

This paper looks at the current realism/antirealism debate in philosophy of science as a dispute between two objectivist interpretations of modern empirical success: Scientific realism and scientific antirealism. The paper traces the debate to a split in responses to the historicist relativism that gained force in the 1960s; it concentrates on the discussions that led to selectivism, a promising realist strategy that focuses on theory-parts rather than whole theories. The paper examines the merits and difficulties of selectivism and argues for a naturalist approach to its present deficiencies, particularly regarding the need for a more precise identification of theory—parts worthy of realist interpretation.

Summary: Responding to Laudan’s skeptical reading of history an influential group of realists claim that the seriously wrong claims past successful theories licensed were not really implicated in the predictions that once singled them out as successful. For example, in the case of Fresnel’s theory of light, it is said that although he appealed to the ether he didn’t actually need to in order to derive his famous experimental predictions—in them, we are assured, the ether concept was “idle,” “inessential,” “peripheral” or worse. This view, developed by J. Worrall and P. Kitcher in the 1980s and subsequently supplemented by J. Leplin and by S. Psillos has received critical attention in the literature over the last decade, but more needs to be said on the subject—or so I suggest in this paper. I bring forward four converging argumentative lines to show how and why, from the days of Fresnel to at least the decade after the Michelson-Morley experiments, the ether functioned and was understood as an “essential” posit in physics. My first line draws Fresnel’s actual deployment of the ether concept and the way he and his circle understood the achievements of his theory. The second line draws is from epistemological assessments of surprising implication in theories and its impact on leading theorists in the last two-thirds of the century. The third line draws from discussions of the optical ether in end-of-century reports circa 1900. The fourth focuses on entrenched metaphysical assumptions that persisted in the practice of physics until the advent of special relativity. Pulling these four lines together shows, I think, why attempts at synchronic identification of sound theory-parts are bound to fail, and also how realists might try to meet the challenge this creates.

The success of a scientific theory T is not an all-or-nothing matter; nor is a theory something one can usually accept or reject in toto (i.e. one may take T as being "approximately true", or take as true just certain "parts" of it, without necessarily affirming every posit and claim specific to T as being either completely right or completely wrong). This, however, raises questions about precisely which parts of T deserve to be taken as approximately true. on the basis of its success. A line of thinkers, particularly Kitcher, Leplin and Psillos, variously look for parts of a theory they can claim to have been "essentially" implicated in its distinctivesuccess, which they regard as primary candidates for realist truth ascription. But, how is one to determine which parts of any theory are "central" or "peripheral", "essential" or "idle" in the required sense? Attempts at spelling out relevant synchronic links between successful predictions and correct partial theorizing increasingly look like a misguided effort. As an alternative, this paper proposes a weaker, but arguably powerful enough, version of the realist relation between success and truth. Focusing on a pivotal case study in recent debates between realists and anti-realists (the conceptual changes undergone by theories oflight in the 19th century), a promising link between success and partial theoretical representation is located in the expansion and stabilization of approximately correct partial theoretical models of the theory's intended domain. The realist link is then formulated accordingly. In the resulting approach (a) predictive success is preserved as a marker of cumulative theoretical gain, but (b) specification of the latter is a diachronic rather than synchronic matter (i.e. gains become clear only after generations of theory change; specification of the particular loci of theoretical gain in connection with a given line of predictive success is not assumed to be generally possible at the time of the success in question). The truth ascriptions that get licensed are partial-of a piece-meal and retrospective sort, focused on methodologically specifiable theoretical subplots from past science.

Recent attempts to turn Standard Quantum Theory into a coherent representational system have improved markedly over previous offerings. Important questions about the nature of material systems remain open, however, as current theorizing effectively resolves into a multiplicity of incompatible statements about the nature of physical systems. Specifically, the most cogent proposals to date land in effective empirical equivalence, reviving old anti-realist fears about quantum physics. In this paper such fears are discussed and found unsound. It is argued that nothing of global skeptical or agnostic significance follows from the kind of underdetermination presently encountered in fundamental quantum theory. The case is instructive, however, for what it shows about the characteristics and prospects of scientific realism as a perspective in contemporary philosophy of science.