We examine Sophie Gibb’s emergent property-dualist theory of mental causation as double-prevention. Her account builds on a commitment to a version of causal realism based on a powers metaphysic. We consider three objections to her account. We show, by drawing out the implications of the ontological commitments of Gibb’s theory of mental causation, that the first two objections fail. But, we argue, owing to worries about cases where there is no double-preventive role to be played by mental properties, her account, (...) which solely affords mental properties a double-preventive role, is incomplete and vulnerable to a causal exclusion objection. We propose a friendly modification to her theory of mental causation that is consistent with her theory’s ontological commitments. Specifically, we sketch an account on which mental properties have a more pronounced causal-structuring role that is not exhausted by the role Gibb assigns them as double-preventers. The result is a novel emergentist theory of mental causation. (shrink)