Intertheoretic Reduction

Philosophers of science since Nagel have been interested in the links between intertheoretic reduction and explanation, understanding and other forms of epistemic progress. Although intertheoretic reduction is widely agreed to occur in pure mathematics as well as empirical science, the relationship between reduction and explanation in the mathematical setting has rarely been investigated in a similarly serious way. This paper examines an important and well-known case: the reduction of arithmetic to set theory. I claim that the reduction is unexplanatory. In defense of this claim, I offer evidence from mathematical practice, and I respond to contrary suggestions due to Steinhart, Maddy, Kitcher and Quine. I then show how, even if set-theoretic reductions are generally not explanatory, set theory can nevertheless serve as a legitimate and successful foundation for mathematics. Finally, some implications of my thesis for philosophy of mathematics and philosophy of science are discussed. In particular, I suggest that some reductions in mathematics are probably explanatory, and I propose that differing standards of theory acceptance might account for the apparent lack of unexplanatory reductions in the empirical sciences.

According to Gold and Stoljar, one cannot both consistently be reductionist about psychoneural relations and invoke concepts developed in the psychological sciences. I deny the utility of their distinction between biological and cognitive neuroscience, suggesting that they construe biological neuroscience too rigidly and cognitive neuroscience too liberally. Then I reject their characterization of reductionism: reductions need not go down past neurobiology straight to physics, and cases of partial, local reduction are not neatly distinguishable from cases of mere implementation. Modifying the argument from unification-as-reduction, I defend a position weaker than the radical, but stronger than the trivial neuron doctrine.

ABSTRACT: 'New wave' reductionism aims at advancing a kind of reduction that is stronger than unilateral dependency of the mental on the physical. It revolves around the idea that reduction between theoretical levels is a matter of degree, and can be laid out on a continuum between a 'smooth' pole (theoretical identity) and a 'bumpy' pole (extremely revisionary). It also entails that both higher and lower levels of the reductive relationship sustain some degree of explanatory autonomy. The new wave predicts that reductions of folk psychology to neuroscience will be located in the middle of this continuum; as neuroscientific evidence about mental states checks in, theoretical folk psychology will therefore be moderately revised. However, the model has conceptual problems which preclude its success in reviving reductionism, and its commitment to a syntactic approach wrecks its attempt to rescue folk psychology. Moreover, the architecture of the continuum operates on a category mistake that sneaks in an eliminativist conclusion. I argue that new wave reductionism therefore tends to be eliminativism in disguise.

This paper challenges a popular thesis which we call the explanatory primitiveness thesis (for short, EPT), namely, the thesis that identities leave no logical space wherein explanatory questions may be formulated and explanatory gaps may reside. We argue that while EPT is, in all likelihood, flawless when the relevant domain consists of identity statements flanked by proper names of individuals it is a mistake to hold that the thesis generalizes to cover all identity statements. In particular, we argue that EPT fails decisively with respect to an important class of identity statements, viz., those in which natural kinds are identified across different theoretical levels (i.e., the so-called inter-level type-identities). If correct, our result shows EPT to be much more limited in scope than is usually supposed. Moreover, and perhaps more significantly, it shows that there is no inherent absurdity in the idea that certain type-identity statements, in particular psychophysical type-identity statements, suffer from an explanatory gap.