Abstract
In “The Best of All Possible Worlds” William E. Mann argues that some possible worlds are morally incommensurable with some others, because some choices are between incompatible alternatives that are themselves incommensurable. The best possible world must be better than, and hence commensurable with, every other world. So if anyone in the actual world ever faces a choice between incompatible alternatives that are morally incommensurable, this is not the best possible world. But it seems that some of us do, on occasion, face such choices. So this is not the best possible world.