First Steps in the stit -Logic Analysis of Intentional Action

We study intentional action in stit-logic. The formal logic study of intentional action appears to be new, since most logical studies of intention concern intention as a mental state. We model an intentional action as an action that possibly deviates from the actual action conducted by an agent. First, an actual action may deviate from an intended action because the agent is not able to carry out the intended action, and the actual action is used as a means to achieve the goal of the intended action. This explains di erences such as the one between the actions `murder' and `manslaughter', and problems like the `dentist's' scenario of Cohen and Levesque. Second, an actual action may deviate from an intended action because the agent's environment behaves unexpectedly and the result of an action is not the one envisaged by the agent. So, the action is unexpectedly unsuccessful. We show how to deal with the distinction between successful and non-successful action by weakening the notion of `knowingly doing' to its `belief' equivalent.