Abstract
Kant’s Categorical Imperative (CI) is to be taken as a necessary and sufficient condition for any action that is permissible, i. e. not prohibited. The class of permissible actions contains actions which are allowed as well as those which are morally required. If to perform an action and to abstain from this action can be taken to be ‘practical opposites’, then an action that is morally required for, a duty, is an action whose practical opposite is prohibited, and vice versa. The class of actions which are merely allowed (neither prohibited nor morally required for) contains all and only those actions who together with their practical opposites belong to the class of permissible (not prohibited) actions. The paper then adduces passages from Kant’s ethical writings on the CI supporting these distinctions.