Most philosophers now accept that an agent may be responsible for an action even though she could not have acted otherwise. However, many who accept such a view about responsibility for actions nevertheless maintain that, when it comes to omissions, an agent is responsible only if she could have done what she omitted to do. If this Principle of Possible Action (PPA), as it is sometimes called, is correct, then there is an important asymmetry between what is required for responsibility (...) for actions and what is required for responsibility for omissions. However, I argue here that PPA is in fact false. It has been advanced on the basis of an insufficiently varied group of examples. Examination of a broader range of cases shows that responsibility for an omission sometimes is, and it sometimes is not, undermined by an inability to have acted. In Sections II and III, I offer two alternative principles to PPA governing ability and responsibility for omissions. (shrink)