 Like any classification, this one is somewhat artificial and arbitrary. Some particular views of supererogation cannot be easily and neatly subsumed under one of its categories. The distinction between (1) and (2) hinges on the nature of the relevant “qualification”: even the rigorous deniers of supererogation are willing to accept some form of excuse for not engaging in particularly difficult or demanding moral action, and qualified supererogationists may often admit that a heroic action is obligatory even if it is unrealistic for society to expect individuals to perform it. The borderline between (2) and (3) is also often vague, since when one tries to explain what makes a class of actions supererogatory, in the unqualified sense of being fully optional, one is often drawn back to the difficulty or risk in performing it, to the particular personal virtue required to do so, or in general terms to certain qualifying conditions which justify leaving them beyond the demands of morality.