Abstract: Last week I watered my plant, causing it to look green and healthy. But this week I failed to water it, causing it to look brown and wilted. My watering the plant was a “positive” event, but what, exactly, was my omission to water it?

Causal claims involving omissions—roughly, events that fail to occur-- are commonplace, but they are puzzling along several dimensions. There is a metaphysical question: what are omissions? There is a semantic question: what do omissive causal claims denote? There is a causal question: do omissions participate in causal relations? And there is a selectivity question: if omissions do participate in causal relations, exactly which ones do? A well-developed metaphysics of omissions will have something to say about each of these questions. Additionally, an ambitious metaphysics of omissions will provide a foundation for resolving several moral issues involving omissions, including moral differences between omissions, and the question of which omissions ground moral responsibility.

My talk defends the view that omissions are de re possibilities of actual events. I argue that an omission is a tripartite metaphysical entity composed of an actual event, a possible event, and a contextually specified counterpart relation between them. I show how the view addresses many of the questions above, and does so better than several existing alternative views on omissions.