Chiao-Li Ou

Symmetrical universes, such as Max Black's famous “two‐sphere” world, are often taken to pose a serious challenge to the universal‐based bundle theory. In response, metaphysicians have either developed more sophisticated versions of the universal‐based account or simply converted to the trope‐based bundle theory. I argue that neither approach is fully satisfactory, for there is a different kind of symmetrical universe, or an alternative interpretation of such universes, that generates comparable challenges to these views. It turns out that neither universal‐based nor trope‐based accounts can fully accommodate symmetrical universes. In light of this, I propose a novel bundle‐theoretic account based on what David Lewis calls “amphibians”—qualities that are neither universals nor tropes—and argue that it accommodates both kinds of symmetrical universes without incorporating unwanted entities, making it preferable to the universal‐based and trope‐based accounts.

I defend a new conception of the particular-universal distinction based on considerations about what David Lewis calls ‘amphibians’. I argue, first, that given the possibility of amphibians, two recently popular conceptions of the particular-universal distinction, namely the repeatability conception and the duplicability conception, are both objectionable since they are biased in one way or another. I then propose a more flexible conception that solves this problem by regarding amphibians as belonging to a sui generis sort of property distinct from what I call ‘strong universals’ and ‘strong tropes’. Finally, I respond to some objections directed at this new account.