This fascinating, if ultimately frustrating, collection of essays addresses "pluralism" in science.  Contributors focus on the foundations of mathematics (Geoffrey Hellman and John Bell), quantum mechanics (Michael Dickson), economics (Esther-Mirjam Sent), the study of behavior (Helen Longino), aspects of biology (Carla Fehr on the evolution of sex, C. Kenneth Waters on genes) and science studies itself (Stephen Kellert).  In addition there is a modest resolution of the mind-body problem (Wade Savage) and a couple of general discussions (Alan Richardson on "the many unities of science" and Ronald Giere on "perspectival pluralism").  Few could claim sufficient expertise to engage with the examples used by all these contributors, but as befits philosophy, it is possible to concentrate on their lessons for the somewhat elusive pluralism that is being advocated by the editors in their introduction.

That introduction begins with the "general idea" of pluralism: "that some phenomena cannot be fully explained by a single theory or fully investigated using a single approach" (p. vii). It sketches the history of philosophical debate from Patrick Suppes' 1978 rejection of a positivist "unity of science", through Nancy Cartwright's advocacy of a "dappled world" of distinct realms governed by a loose patchwork of laws and John Dupré's "promiscuous realism" with its unlimited number of equally acceptable ways of classifying the contents of the world, to present concerns for the variety of epistemic virtues displayed by the sciences and the inescapability of interdisciplinarity.  The editors usefully contrast plurality in the sciences — the use of different and often conflicting models, theories, explanatory strategies etc. to address particular scientific questions — with pluralism about science ­– roughly that plurality is to be applauded rather than tolerated for the time being as our inadequate response to the complexity of the one world.  But as they note, even those who advocate some sort of pluralism differ as to its content, range, and implications.

Opposed to all these pluralisms is the monism of the majority of philosophers: the idea that there is indeed just one world that ultimately works together in a unified way.  God, one might say, knows just one set of laws of nature, not a patchwork.  We may not be able to discover these laws, we may have to tolerate plurality even in the long run, but our synoptic philosophy assures us that this would be second-best. 

Despite the editors' assurance that their contributors espouse pluralism, my reaction to many of the essays was that monism was not really put at risk.  Given the avowedly epistemological rather than metaphysical focus of the collection, there was often the thought that what were offered as pluralities of explanatory theory could in fact be reconciled in one more comprehensive account.  The more so, perhaps, because the epistemology on offer tends to be purely descriptive rather than philosophically revisionary. 

To illustrate these claims, one might take Fehr on the evolution of sex.  She contrasts three explanations for the existence and maintenance of sexual reproduction.  The Red Queen (RQ) explanation says sex is beneficial because its exchange of DNA allows organisms "to stay adapted to a continually changing biotic environment" (p. 168).  Its elaboration involves the idea that sexually reproducing organisms stay ahead of their parasites; sex will be found more often in environments where parasite pressure is stronger.  Muller's Ratchet describes a process whereby asexual populations regularly lose their least mutated line and so eventually disappear entirely; sexual reproduction on the other hand allows a population to recover its least mutated forms.  The DNA Repair explanation says that the biochemistry of meiosis allows organisms to repair genome damage.  Noting some difficulties with the first two, population-focused accounts, Fehr mentions some theorists who have argued for a combination of these views and says herself

Currently the DNA Repair explanation can be used to account for meiosis and the RQ can be used to account for outcrossing.  Sex in some domains will be explained by a constellation of explanations that includes the RQ and not DNA Repair, in other domains by a constellation that includes DNA Repair and not the RQ, and in yet others by a constellation that includes both, or, for that matter, neither (p. 173).

Fehr spends a good deal of space trying to convince us that these three explanations must be viewed pluralistically rather than as partial accounts of very different aspects of the existence of sexual reproduction.  They operate within different frameworks, different sub-disciplines; they pick on processes at different levels of organization; they abstract different aspects of sex.  She says that the DNA Repair model abstracts away from individual variation, while the RQ highlights that same variation; each explanation ignores what is crucial for the other.  But I do not see why we should think that this is a matter of obscuring (cf. p. 187) the aspects of sex accounted for by the other model; it is simply ignoring it. 

Again Waters on gene-centered biology versus its critics tells us that the gene-centered research obviously leaves certain important factors out of account.  An ideology of monism apparently leads its opponents to denigrate the successes of gene-centered work and advocate its replacement by developmental systems theory, and equally leads the main-stream to take an exaggerated view of the role of genes.  But one's response, and indeed Waters' own, is surely to say that things are more complicated than the gene-centered people assume but that they have, within their limits, made worthwhile progress.  A more comprehensive picture would incorporate their results rather than wipe the slate clean.  He insists that there are too many aspects of biological development to be comprehended by one simple theoretical approach to investigation, but this is pluralism for the practice of biology rather than pluralism for the biological reality being investigated.

The same monistic resolution is apparent in the joint paper on mathematics.  Intuitionism versus classical mathematics is construed not as a conflict over the one true logic and mathematics but as a different focus of interest:

Classical reasoning is especially useful in scientific, as well as purely mathematical, contexts in which we are interested in what holds or would hold in a certain situation or model, given certain assumptions, as an objective matter regardless of computability…. However, if computability or constructivity is our goal, then obviously it will not be achieved unless we modify our rules, and we may even introduce a new language (also rooted in ordinary language) as intuitionism does…. Moreover, as both purposes–truth-preservation simpliciter and constructive interpretability–are worthy and important, we should certainly have peaceful coexistence and even cooperation (p. 69).

The second half of their paper proposes a pluralist ontology for mathematics, by contrast to the natural sciences, since "After all, we live in a unique world, don't we?" (p. 76).  I think it is the epistemological focus, and thus the general lack of attention to what their pluralisms would imply for the make-up of that unique world, that makes most of the essays less than convincing as support for the editors' position.  Giere does, however, spend some time on the metaphysical implications of monism/pluralism, and argues that these issues are better taken methodologically, thereby leaving the metaphysical issues unresolved.

Savage invokes pluralism in his very interesting reaffirmation of a mind-brain identity theory, but in the end he is non-committal on what his position amounts to in this regard. One central plank in his argument is the defense of a distinction between two types of identity, empirical and logical.  The meat of his paper lies in its careful rebuttal of the appeal to Leibniz' law and to Kripke's arguments against the very possibility of such mind-brain identity.  The appeal to Leibniz is to the effect that mental items, pains, or whatever, have qualities that are not possessed by physical processes, so they cannot be identical with them.  Savage responds by saying that Leibniz' law applies to the logical relation of identity but not to empirical identity: water, for instance, is spatially continuous and thus cannot be identical with a collection of molecules; an appeal to Leibniz' law prior to empirical investigation would for ever rule out the fruitful identifications chemistry has been able to make. 

He responds to Kripke on two levels.  Accepting some of Kripke's machinery, he argues that in statements like "pain is neural excitation" one of the referring expressions at least is not rigid, contrary to Kripke's assumptions.  But he also has a more far-reaching argument that rejects Kripke's central claim about identity, regarding it as designed for logical not empirical identities. As in the Leibniz argument, Savage maintains that "water is H₂O" is conceivably false, and so not one of Kripke's notorious necessary a posteriori truths: it might have turned out to be a continuous fluid or gelatinous globules.  I do not have space to report the detailed moves in Savage's argument, but it certainly seems worthy of very careful attention.

So, overall, we have a variety of interesting discussions of current problems in a range of sciences and in science studies, emphasizing the apparent inescapability of pluralist approaches.  Whether they add up to an endorsement of pluralism as our preferred approach to epistemological, methodological, and ultimately metaphysical questions, I think is dubious, but as Suppes' early contribution showed, the empirical facts of current science do not make unreflective monism easy.  More work is needed, and this volume should help to catalyze it.

References

Nancy Cartwright (1999).  The Dappled World: Studies of the Boundaries of Science.  Cambridge: Cambridge University Press.

John Dupré (1993). The Disorder of Things: Metaphysical Foundations of the Disunity of Science.  Cambridge, Mass.: Harvard University Press.

Patrick Suppes (1978). "The Plurality of Science."  In PSA 1978: Proceedings of the 1978 Biennial Meeting of the Philosophy of Science Association, vol. 2, ed. Peter Asquith and Ian Hacking, 3-16.  East Lansing: Philosophy of Science Association.

© 2007 Ed Brandon

Ed Brandon is, by training, a philosopher, and now is working in a policy position in the University of the West Indies at its Cave Hill Campus in Barbados.

Categories: Philosophical