Bohr meets Rovelli: a dispositionalist account of the quantum limits of knowledge

Abstract

I begin by examining the question of the quantum limits of knowledge by briefly presenting the constraints of the theory that derive from its mathematical structure (in particular the no-go theorems formulated by von Neumann and Kochen and Specker). I then argue that these theorems reflect on a formal level those practical and experimental settings that are needed to come to know the properties of physical systems. In particular, I discuss some aspects of this relationist and contextualist conception of reality by comparing, in their apparent diversity, Bohr’s holistic, and Rovelli’s relationist interpretation of the formalism, that deep down share a unifying metaphysics of dispositions and propensities. Both interpretations are based on the widely shared fact that quantum mechanics does not describe previously definite quantities. In the final part, I show that, as a consequence of a relationist and perspectival approach to quantum mechanics, the quantum state of the universe regarded as an isolated system cannot be known in principle, so that the universe must be described “from within” by dividing it into two arbitrary parts. This is in fact the only way in which the two systems can exchange information by being physically correlated.