
185On Kinds of Indiscernibility in Logic and MetaphysicsBritish Journal for the Philosophy of Science 63 (1): 2784. 2012.Using the HilbertBernays account as a springboard, we first define four ways in which two objects can be discerned from one another, using the nonlogical vocabulary of the language concerned. Because of our use of the HilbertBernays account, these definitions are in terms of the syntax of the language. But we also relate our definitions to the idea of permutations on the domain of quantification, and their being symmetries. These relations turn out to be subtlesome natural conjectures abo…Read more

116In a series of recent papers, Simon Saunders, Fred Muller and Michael Seevinck have collectively argued, against the folklore, that some nontrivial version of Leibniz's principle of the identity of indiscernibles is upheld in quantum mechanics. They argue that all particlesfermions, paraparticles, anyons, even bosonsmay be weakly discerned by some physical relation. Here I show that their arguments make illegitimate appeal to nonsymmetric, i.e.~permutationnoninvariant, quantities, and …Read more

97The role of symmetry in the interpretation of physical theoriesStudies in History and Philosophy of Science Part B: Studies in History and Philosophy of Modern Physics 52 (Part B): 153162. 2015.The symmetries of a physical theory are often associated with two things: conservation laws and representational redundancies. But how can a physical theory's symmetries give rise to interesting conservation laws, if symmetries are transformations that correspond to no genuine physical difference? In this article, I argue for a disambiguation in the notion of symmetry. The central distinction is between what I call "analytic" and "synthetic" symmetries, so called because of an analogy with analy…Read more

67How best to think about quantum systems under permutation invariance is a question that has received a great deal of attention in the literature. But very little attention has been paid to taking seriously the proposal that permutation invariance reflects a representational redundancy in the formalism. Under such a proposal, it is far from obvious how a constituent quantum system is represented. Consequently, it is also far from obvious how quantum systems compose to form assemblies, i.e. what i…Read more

43The purpose of this short article is to build on the work of Ghirardi, Marinatto and Weber and Ladyman, Linnebo and Bigaj, in supporting a redefinition of en tanglement for “indistinguishable” systems, particularly fermions. According to the proposal, nonseparability of the joint state is insufficient for entanglement. The re definition is justified by its physical significance, as enshrined in three biconditionals whose analogues hold of “distinguishable” systems.

42In this article I expound an understanding of the quantum mechanics of socalled “indistinguishable” systems in which permutation invariance is taken as a symmetry of a special kind, namely the result of representational redundancy. This understand ing has heterodox consequences for the understanding of the states of constituent systems in an assembly and for the notion of entanglement. It corrects widespread misconceptions about the intertheoretic relations between quantum mechanics and both …Read more