Physical Computation

Abstract

This chapter is a primer on physical computation. It distinguishes between abstract and concrete computation. It introduces the notion of simulation of one physical system by another and the more specific notion of computational simulation of a physical system by a computing system. It introduces the problem of distinguishing between physical processes that count as computations and physical processes that don’t, as well as other desiderata of an adequate account of physical computation. It introduces pancomputationalism, which is the most liberal way of drawing a boundary. It introduces different accounts of concrete computation—mapping accounts, semantic accounts, and mechanistic accounts—and explains that the robust mapping account developed in subsequent chapters can improve upon and be integrated with the three families of accounts. Finally, it introduces the physical Church-Turing thesis, according to which any physically computable function is computable by Turing machines.