Representational conventions and invariant structure

Abstract

In the philosophical literature, symmetries of physical theories are most often interpreted within the general doctrine called 'Sophistication'. Roughly speaking, it says that models related by symmetries can peacefully co-exist while representing the same physical possibility. But this interpretation still leaves open two main worries about Sophistication: (a) it allows the individuation of what I call 'structure-tokens' to remain intractable and thus of limited use, which is why practising physicists frequently invoke 'relational, symmetry-invariant observables'; and (b) it leaves us with no formal framework for expressing counterfactual statements about the world. Here, I will show that a new Desideratum to be satisfied by theories with symmetries answers these worries. The new Desideratum is that the theory admits what I will call representational conventions for its structure-tokens.