 Yet physicalists need not maintain that everything strongly globally supervenes upon the physical. Many physicalists want to allow that the existence of things like ghosts and Cartesian souls is logically compatible with the physical facts of our world. They think that there actually aren’t any such things, not that there could not be any, or even that there logically could not be any given the physical facts of our world. They thus allow that two worlds could be physical duplicates, but nonetheless differ mentally—two worlds that are physically just alike, but only one of which contains a community of disembodied spirits. (Note that because the worlds are physical duplicates, those spirits either exert no causal influence on the physical at all, or else only exert redundant, “overdeterministic” causal influence on the physical.)