Anselm's Logic of Agency Sara Uckelman Abstract: The origins of treating agency as a modal concept go back at least to the 11th century when Anselm, Archbishop of Canterbury, provided a modal explication of the Latin _facere_ 'to do', which can be formalized within the context of modern modal logic and neighborhood semantics. The agentive logic induced by his conception satisfies the traditional square of opposition, but also has some unique properties which reflect the fact that Anselm's modal view of agency is grounded strongly in nonlogical philosophical and theological considerations. Our conclusion is that Anselm's logic of agency when presented with the tools of modern formal logic is still a viable theory of agency for current times. Keywords: agency; square of opposition; ordinary language; neighborhood semantics; Anselm of Canterbury