(De=obligation + logical) A deontological ethics is one that claims that it is something in the nature or structure of actions that makes them obligatory or impermissible (essentially ignoring consequences). Kant's categorical imperative ("act so that the maxim of your action could be a law for all rational beings") is often though to be a deontological rule. Kant once remarked that if a killer asks where your friend is, you have to tell him the truth. See teleological.