Abstract

Externalism says that many ordinary mental contents are constituted by relations to things outside the mental subject’s head. An infl uential objection says that externalism is incompatible with our commonsense belief in mental causation, because such extrinsic relations cannot play the important causal role in producing behavior that we ordinarily think mental content plays.An extremely common response is that it is simply obvious, from examples of ordinary causal processes, that extrinsic relations can play the desired causal role. In this paper I argue that such examples show no such thing, and that the only reason to think they do is to endorse an unacceptable principle concerning the sufficient conditions for causal efficacy. Internalists might be wrong that externalism is incompatible with mental causation; but the most common defense against that allegation should not move us at all.