Theory-Change And The Logic Of Enquiry: New Bearings In Philosophy Of Science

Review of Metaphysics, The, Sept, 1999 by Christopher Norris

Thus for Quine, famously, knowledge is "a man-made fabric which impinges on experience only along the edges," or again, "a field of force whose boundary conditions are experience."(14) At the center of the fabric are those so-called logical laws of thought (bivalence, noncontradiction, excluded middle) Which are taken to possess a priori validity or to function as the very ground rules of rational debate in the physical sciences and elsewhere. However, Quine cautions, we should not be misled into thinking that these rules are absolutely or intrinsically immune from revision. For this is after all just another doomed attempt to uphold the artificial dichotomy--whether Humean, Leibnizian, Kantian, Carnapian, or whatever--between contingent matters of fact on the one hand and necessary truths of reason on the other. "Taken collectively," Quine writes, "science has its double dependence upon language and experience; but this duality is not significantly traceable into the statements of science taken one by one."(15) And again, pushing the argument through: "That there is such a distinction to be drawn at all is an unempirical dogma of empiricism, a metaphysical article of faith."(16) Rather, what we feel ourselves bound to accept as logical laws of thought should instead be treated as particularly well-entrenched precepts, principles, or procedural guidelines which have so far proved to have great utility in working some manageable structure into the otherwise chaotic flux of incoming sensory stimuli. Any conflict at the edges of the fabric (that is, any recalcitrant experience or item of anomalous observation data) can always be assuaged by making certain adjustments elsewhere in the system, or by redistributing predicates and truth values so as to restore equilibrium. At times this process may go so far--under pressure of conflicting empirical evidence--that it forces a change at or very near the logical heart of the fabric, that is to say, a revision to the hitherto sacrosanct laws of thought. Thus "[a]ny statement can be held true, come what may, if we make drastic enough adjustments elsewhere in the system,"(17) And the same applies to those physical objects which we tend to think of as existing out there beyond the boundary of the fabric, but which in fact, Quine argues, should rather be viewed as so many posits whose being is dependent on our various theories, ontologies, descriptive languages, conceptual schemes, and so forth.

No doubt, instrumentally speaking, the "conceptual scheme of science" is a useful tool "for predicting future experience in the light of past experience." Yet this should not deceive us into thinking that the objects posited by science--from quarks and gluons, via electrons, atoms and molecules, to the whole range of middling and large-scale objects--are more or less real according to some ultimate, non-scheme-dependent standard of objective truth. For what, after all, could such a standard consist in if not our current best notions of reality derived from a mixture of commonsense wisdom plus other, more specialized and preferably up-to-date items of scientific knowledge? In which case--given the presumed nonfinality or the always revisable status of science as we have it--there is simply no distinguishing between various posits (from centaurs and Homer's gods, via numbers, mathematical classes or sets, to brick houses on Elm Street) in point of ultimate reality or truth. Rather, as Quine puts it,