Anselm's logic of agency

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 non-logical philosophical and theological considerations. We show that the logic modeling Anselm’s theory of agency provides an interesting alternative to standard logics of agency based on stit-theory.