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Intentions and Unified Agency: Insights from the Split-brain Phenomenon


  • Many thanks to Louise Antony, Esa Diaz-Leon, Heather Logue, Jennifer Matey, Bénédicte Veillet, and to two anonymous referees and an editor at Mind & Language for helpful comments on drafts of this article.

Address for correspondence: Department of Philosophy, Washington University in St. Louis, Campus Box 1073 One Brookings Drive, St. Louis, Missouri, 63130–4899, USA.



Under experimental conditions, behavior suggesting dual agency is easily elicited from split-brain subjects who usually behave in an unremarkable fashion. This article presents a model of split-brain agency that accounts for this apparent tension. Right and left hemisphere are associated with distinct agents, R and L, each of whose unity is grounded in the special inferential and experiential relations that its mental states bear to each other. These same relations do not hold interhemispherically; rather, unified behavior is largely the result of a split-brain subject's having a single body, much of whose coordination in action is maintained by forces operating downstream of reasons and intentions and conscious experiences. The split-brain subject as a whole is still a unified agent as well, however, in virtue of R's and L's intentions bearing, with respect to one and the same body, those special causal powers that an individual's intentions (and hers alone) bear to her body (and to her body alone).