  We now appear to have an interesting situation. Quantum mechanics is compatible with two distinct metaphysical ‘packages’, one in which the objects are regarded as individuals and one in which they are not. Thus, we have a form of ‘underdetermination’ of the metaphysics by the physics (see van Fraassen 1985 and 1991; French 1989; Huggett 1997). This has implications for the broader issue of realism within the philosophy of science. If asked to spell out her beliefs, the realist will point to currently accepted fundamental physics, such as quantum mechanics, and insist that the world is, at least approximately, however the physics says it is. Of course, there are the well-known problems of ontological change (giving rise to the so-called Pessimistic Meta-Induction) and Underdetermination of Theories by the Empirical data. However, this underdetermination of metaphysical packages seems to pose an even more fundamental problem, as the physics involved is well entrenched and the difference in the metaphysics seemingly as wide as it could be. These packages support dramatically different world-views: one in which quantum objects, such as electrons, quarks and so forth, are individuals and one in which they are not. The realist must then face the question: which package corresponds to the world? 