Action, Failure and Free Will Choice in Stit Logic

Abstract

The central axiom of stit theory is independence of agency. This axiom states that simultaneous choices of different agents are independent in the sense that a choice of one agent cannot impair the choice making capacity of other agents. The axiom of independence can then be said to express freedom of choice.1 But freedom of choice is different from freedom of will or freedom of action. In this paper we will suggest how to formally study the differences between freedom of choice, freedom of will and freedom of action. To do so, we will extend stit theory with agent specific epistemic operators thereby introducing the subjective viewpoint into logics for agency. We argue that only by introducing this subjective viewpoint we can formalize free will choice and the distinctions between choosing, acting and failing.