Saying, "if Mary had watered Sam's plant, it wouldn't have died," is an ordinary way to identify Mary not watering Sam's plant as the cause of its death. But there are problems with this statement. If we identify Mary's omitted action as the cause, we seemingly admit an inordinate number of omissions as causes. For any counterfactual statement containing the omitted action is true (e.g. if Hillary Clinton had watered Sam's plant, it wouldn't have died). The statement, moreover, is mysterious because it is not clear why one protasis is more salient than any alternatives such as "if Sam hadn't gone to Bismarck." In the burgeoning field of experimental metaphysics, some theorists have tried to account for these intuitions about omissive causes. By synthesizing this data and providing a few experiments, I will suggest that judgments - and maybe metaphysics - about omissive causes necessarily have a normative feature. This understanding of omissive causes may be able to adequately resolve the problems above.