Emergence, Reduction and Supervenience: a Varied Landscape

TL;DR

This paper explores the complex relationships between emergence, reduction, and supervenience, arguing that emergence can occur independently of reduction and supervenience, with implications for understanding philosophical and scientific theories.

Contribution

It clarifies the logical independence of emergence from reduction and supervenience, defending Nagelian reduction and analyzing their interrelations.

Findings

Emergence can occur with or without reduction.

Supervenience is reducible to deduction via Beth's theorem.

Examples show supervenience without emergence and vice versa.

Abstract

This is one of two papers about emergence, reduction and supervenience. It expounds these notions and analyses the general relations between them. The companion paper analyses the situation in physics, especially limiting relations between physical theories. I shall take emergence as behaviour that is novel and robust relative to some comparison class. I shall take reduction as deduction using appropriate auxiliary definitions. And I shall take supervenience as a weakening of reduction, viz. to allow infinitely long definitions. The overall claim of this paper will be that emergence is logically independent both of reduction and of supervenience. In particular, one can have emergence with reduction, as well as without it; and emergence without supervenience, as well as with it. Of the subsidiary claims, the four main ones (each shared with some other authors) are: (i): I defend the traditional Nagelian conception of reduction (Section 3); (ii): I deny that the multiple realizability argument causes trouble for reductions, or "reductionism" (Section 4); (iii): I stress the collapse of supervenience into deduction via Beth's theorem (Section 5.1); (iv): I adapt some examples already in the literature to show supervenience without emergence and vice versa (Section 5.2).