My interest in reductive explanation arises from my PhD research on fundamentality: the idea that there is a level of basic scientific facts on which all facts are grounded. A key question I set out to answer is how we can distinguish the fundamental level from the non-fundamental level. For example, if we are considering a Newtonian world (a world in which Newtonian mechanics is true), by what criteria do we say that facts involving only atoms and their basic physical properties are fundamental, whereas facts involving composite objects and their high-level properties are non-fundamental? My dissertation answers this question by defending two claims about fundamentality: that fundamentality is closely linked to reductive explanation; and that reductive explanation is best understood in terms of a priori entailment.
Reductive explanations are a type of explanation common in the sciences, which enable us to understand why features of the explananda exist in worlds containing the explanantia. In doing so, they illuminate why the explananda are grounded in the more fundamental explanantia. Thus, we can say that non-fundamental facts involving Newtonian composites and their properties obtain in virtue of fundamental facts involving Newtonian atoms and their properties, provided that the former can be reductively explained in terms of the latter (and not vice versa).
Given this account of fundamentality, an adequate account of reductive explanation will advance our philosophical understanding of fundamentality. My dissertation evaluates deducibility theories of reductive explanation. Roughly, deducibility theories state that X reductively explains Y if and only if Y is deducible from X in conjunction with additional assumptions Z. Different deducibility theories will provide different accounts of deduction, and different accounts of the content of Z. In my PhD I used case studies of reductions in physics to problematize one class of deducibility theories and to defend another. I argued that modern Nagelian theories of reduction (such as the Generalised Nagel-Schaffner model) struggle to model these reductive explanations. Meanwhile, I argued that a priori entailment based theories successfully model and better illuminate these explanations. I have recently published these ideas in light of one of my case studies, the reductive explanation of mass additivity:
This research is also discussed in section 6.15 of David Chalmers’ (2012) Constructing the World (Oxford University Press).
I am currently working on another paper that defends the a priori entailment theory of reduction. This paper focuses on how the content of the special sciences is a priori deducible from the descriptions and theories of physics. In particular, I answer the question of how there could be a priori entailment relations between different levels of description even when the descriptions have significantly different theoretical content. Particular attention is made to reductive explanations of phase changes.
More to come as this research progresses!