 This brief sketch of possible types of metaphysical explanations of supervenience barely scratches the surface. Among the many other options, replies grounded in appeals to tropes or universals have garnered explicit attention (Ridge 2007, Suikkanen 2010). As with the appeal to grounding, a central question about such strategies is whether they constitute genuine explanatory progress, or whether they simply explain one necessity by appealing to some further brute necessity.