There is an important contemporary debate in moral responsibility about whether the following asymmetry thesis is true: moral responsibility for actions does not require alternative possibilities but moral responsibility for omissions does. In this paper, we do two things. First, we consider and reject a recent argument against the asymmetry thesis, contending that the argument fails because it rests on a false view about the metaphysics of omissions. Second, we develop and defend a new argument against the asymmetry thesis, one (...) that avoids the problem with the first argument by not resting on any assumptions about what omissions are metaphysically. (shrink)