Intertheoretic reduction: a new look at an old project

Abstract

This thesis argues that the core idea of intertheoretic reduction in science is still defendable. The thesis is divided into three parts. In Part One, comprising five chapters, a positive account of reduction is discussed. In Chapter 1， Nagel's classic account of reduction is considered. There are two central themes in this survey: Nagel's account of bridge principles and his non-formal conditions. The former shows that bridge principles are not limited to identity statements, while the latter shows that almost all later philosophers (whether reductionists or anti-reductionists) have ignored these central conditions of reduction. In Chapter 2, the first wave of objections to Nagel's account, including the problems of meaning variance and inconsistency, are central issues. It will be argued that the former is not a serious objection. However, the latter leads us to Chapter 3, in which reductionists' responses to the problem of inconsistency are considered. The main tool used to remove the problem of inconsistency is the notion of approximation. I defend approximate reduction, but it needs further metaphysical clarifications to survive the second wave of objections. Before these metaphysical points are addressed, the rest of Chapter 3 is devoted to showing that identity statements between things are one kind, but not the only acceptable kind, of bridge principle, and that identity statements between properties are not required for reduction. The central notion in the second wave of objections against reduction is 'multiple realization'. In Chapter 4, I present a causal analysis of properties and realization, and show that (a) a version of the unity of science is defendable within the causal framework, and (b) arguments against the possibility of general and autonomous special sciences are not valid. In Chapter 5, an alternative flat analysis of properties and realization, based on the notion of similarity, is discussed. Firstly, I argue that this alternative can save a version of the unity of science. Secondly, I show that both of the discussed metaphysical analyses remove the second wave of objections against reduction. Part Two, comprising three chapters, concerns negative accounts of reduction. In Chapter 6, explanatory reduction is critically analyzed. I argue that the contrastive nature of explanation prevents us defining reduction in terms of explanation. In Chapter 7, those accounts of reduction which define it in terms of supervenience are discussed. I argue that supervenience is not even a necessary condition of reduction. Chapter 8 is devoted to considering functional reduction, which defines the reduction of a property to a domain of more basic properties. Based on two possible ways of functionalization, the inadequacy of functional reduction is discussed. Finally, in Chapter 9 of Part Three, I return to the version of reduction that I defend. This has two important components: approximation and non-formal conditions. First, I sketch a portrait of this account, and then I consider some of its features, such as its aim and relata, its non-formal nature and its direction.