Are Enabling and Allowing Harm Morally Equivalent?

It is sometimes asserted that enabling harm is morally equivalent to allowing harm (the moral equivalence thesis). In this article, I criticize this view. Positively, I show that cases involving self-defence and cases involving people acting on the basis of a reasonable belief to the effect that certain obstacles to harm will remain in place, or will be put in place, show that enabling harm is harder to justify than allowing it. Negatively, I argue that certain cases offered in defence of the moral equivalence thesis fail, because either (1) their similarity with the archetypal trolley case limits their relevance to an assessment of this thesis, or (2) they are compromised by their reliance on the elusive notion of a situation being completely stable.