Unthinkable actions

For each person, some actions are unthinkable: performing them requires crossing a line that one's conscience cannot allow crossing. This article explores what such unthinkability is. In doing so, it introduces a novel categorization of theories of action and practical reason. The article argues that an action is unthinkable if and only if the agent judges that she should never treat any consideration as a reason in favor of performing this action. This view meets two important tests. The first is ‘Failure’: a theory of unthinkable action must allow for the conceptual possibility of doing the unthinkable and explain what is special about the failure implicated in doing the unthinkable, especially in comparison to the failure implicated in akratic action. The second is ‘Incapacity’: a theory of unthinkability must distinguish between not doing something because it is unthinkable and not doing something because of an extremely negative psychological reaction.