  Matters aren’t so simple, however. “I ought to return John’s gun” (since I promised to return it) and “I ought not to return John’s gun” (since he is no longer in his right mind) do not entail “I can both return the gun and not return it.” So why think that if I ought to worship the first god and I ought to worship the second, I ought to worship both of them? Because the two cases are dissimilar. In the first, neither obligation is indefeasible; each can, in principle, be trumped by other stronger obligations. While I indeed have prima facie obligations both to return the gun and to not return it, the only actual obligation I have in the circumstances that were described is the obligation to not return the gun. Because “I ought to return the gun and I ought not to return the gun (that is, I have a prima facie obligation to return it and a prima facie obligation to not return it)” does not entail “I have an actual obligation both to return and to not return the gun,” there is no reason to infer that I can do both. By contrast, both of the obligations referred to in 7 are indefeasible. (Their indefeasibility appears to be part of the very concept of divine worship; part of what it means to be God is to be such that no other obligation can take precedence over our obligation to be totally devoted and unconditionally committed to him.) Both are therefore actual, and not merely prima facie, obligations. Now even though one can have a prima facie obligation to do something one is unable to do, it is doubtful that one can have an actual obligation to do something one can’t do. That I am obligated to worship both deities thus seems to entail that I can worship both deities. The inference from 6 to 7 seems sound.