Autonomy of Theories: An Explanatory Problem

This paper aims to draw attention to an explanatory problem posed by the existence of multiply realized or universal behavior exhibited by certain physical systems. The problem is to explain how it is possible that systems radically distinct at lower-scales can nevertheless exhibit identical or nearly identical behavior at upper-scales (typically everyday length and time scales). Theoretically this is reflected by the fact that continuum theories such as fluid mechanics are spectacularly successful at predicting, describing, and explaining fluid behaviors despite the fact that they do not recognize the discrete (atomic/molecular) nature of fluids. A standard attempt to reduce one (continuum) theory to another (atomic/molecular theory), is shown to fail to answer the appropriate question about autonomy.