Some Worlds of Quantum Theory

This paper assesses the Everettian approach to the measurement problem, especially the version of that approach advocated by Simon Saunders and David Wallace. I emphasise conceptual, indeed metaphysical, aspects rather than technical ones; but I include an introductory exposition of decoherence. In particular, I discuss whether -- as these authors maintain -- it is acceptable to have no precise definition of 'branch' (in the Everettian kind of sense).