This paper discusses the inefficacy problem that arises in contexts of “collective harm.‘ These are contexts in which by acting in a certain sort of way, people collectively cause harm, or fail to prevent it, but no individual act of the relevant sort seems to itself make a difference. The inefficacy problem is that if acting in the relevant way won’t make a difference, it’s unclear why it would be wrong. Each individual can argue, “things will be just as bad (...) whether or not I act in this way, so there’s no point in doing otherwise.‘ The goal of this paper is to give an overview of some of the main responses available to the problem and to highlight central issues that arise for each type of response. In the final section, I explain what I take to be the most promising strategy and discuss the form that this strategy should take. (shrink)