How Downwards Causation Occurs in Digital Computers

TL;DR

This paper examines how high-level algorithms in digital computers exert downward causation on physical hardware, explaining the mechanism that allows strong emergence despite the causal completeness of physics.

Contribution

It clarifies the mechanism enabling strong emergence and downward causation in digital computers, addressing the apparent conflict with physical causal completeness.

Findings

High-level programs control physical hardware states.

Strong emergence occurs through specific causal mechanisms.

Diachronic emergence is generally not possible due to causal effectiveness of higher levels.

Abstract

Digital computers carry out algorithms coded in high level programs. These abstract entities determine what happens at the physical level: they control whether electrons flow through specific transistors at specific times or not, entailing downward causation in both the logical and implementation hierarchies. This paper explores how this is possible in the light of the alleged causal completeness of physics at the bottom level, and highlights the mechanism that enables strong emergence (the manifest causal effectiveness of application programs) to occur. Although synchronic emergence of higher levels from lower levels is manifestly true, diachronic emergence is generically not the case; indeed we give specific examples where it cannot occur because of the causal effectiveness of higher level variables.