Topos Theoretic Quantum Realism

Abstract

Topos Quantum Theory (TQT) is standardly portrayed as a kind of ‘neo-realist’ reformulation of quantum mechanics. In this paper, we study the extent to which TQT can really be characterised as a realist formulation of the theory, and examine the question of whether the kind of realism that is provided by TQT satisfies the philosophical motivations that are usually associated with the search for a realist reformulation of quantum theory. Specifically, we show that the notion of the quantum state is problematic for those who view TQT as a realist reformulation of quantum theory.