Abstract

I argue that, in order for us to be justified in believing that two theories are metaphysically equivalent, we must be able to conceive of them as unified into a single theory, which says nothing over and above either of them. I propose one natural way of precisifying this condition, and show that the quantifier variantist cannot meet it. I suggest that the quantifier variantist cannot meet the more general condition either, and argue that this gives the metaphysical realist a way to rule out theses like quantifier variance without appealing to fundamentality, grounding, or "levels" of reality.