Flat-footed functionalism in the face of T-duality

The goal of this paper is to examine the viability of Lewis-style spacetime functionalism in the presence of string theory duals. This task is carried out in three steps. First, I discuss Lewisian functionalism, and the related Geneva plan, bringing to light a number of features that are far too often passed over without comment in the literature on philosophy of physics. Then I show that Lewis-style functionalism fails as an account of spacetime emergence in the presence of certain theory duals, by investigating a simple toy case involving string theories related by T-duality. I find that the functionalist ought to, if she takes her functionalist commitments seriously, identify terms related via the duality map as they refer to the same functional roles. This blocks the argument that spacetime is emergent. However, this might just as well be interpreted as a success—spacetime functionalism implies a deflationary interpretation of T-duality. Finally, I offer a brief look forward by examining whether there is a positive case to be made for the deflationary interpretation, which I refer to as flat-footed functionalism. I find that it is a surprisingly promising account, with several good points in its favour. However, the position is not without its issues, and remains underdeveloped.