Abstract:  Jaegwon Kim has argued that unless mental events are reducible to subvening physical events, they are at best overdeterminers of their effects. Recently, nonreductive physicalists have endorsed this consequence claiming that the relationship between mental events and their physical bases is tight enough to render any such overdetermination nonredundant, and hence benign. I focus on instances of this strategy that appeal to the notion of constitution. Ultimately, I argue that there is no way to understand the relationship between irreducible mental events and their physical bases such as to both eliminate causal redundancy and preserve the efficacy of mental events.