  Mills says that this argument is invalid, because a physical event can have features not explained by the event which is its sufficient cause. For example, “the rock’s hitting the window is causally sufficient for the window’s breaking, and the window’s breaking has the feature of being the third window-breaking in the house this year; but the facts about prior window-breakings, rather than the rock’s hitting the window, are what cause this window-breaking to have this feature.”