  Moreover, Socrates cannot try to define justice by enumerating the  types of action that justice requires or forbids. We might have  objected to this strategy for this reason: because action-types can  be specified in remarkably various ways and at remarkably different  levels of specificity, no list of just or unjust action-types could  be comprehensive. But a specific argument in Book One suggests a  different reason why Socrates does not employ this strategy. When  Cephalus characterizes justice as keeping promises and returning what is owed, Socrates objects by citing a case in which returning what is owed would not be just (331c). This objection potentially has very  wide force, as it seems that exceptions could always be  found for any action-type that does not include in its description a  word like ‘wrong’ or ‘just’. Wrongful killing may always be wrong, but is killing? Just recompense may always be  right, but is recompense?