The right to commit homicide in self-defense is not sui generis, a case alone unto itself. It is rather one case within a range of morally and legally justified defensive actions. It is a range which might properly include defending one's position in a queue by delivering some sharp words to an interloper, defending a valuable art work by striking a thief who is about to steal it, through to defending one's life by shooting and killing an assailant who is about to kill you. If we are able to develop a model which explains the full range of justified defensive acts in terms of an underlying moral structure, this will have great value, especially when we come to discuss the application of defensive rights to war. The requirements for such a model will be that it explains, as fully as possible, the complete class of justified defensive actions and illuminates the limitations and criteria that characterize their operation.
We have seen in the last chapter that self-defense is a specific liberty to commit homicide in the context of a background presumption against such acts. Hohfeld treats liberties as a normative relation between three elements, namely: subject (the party who possesses the liberty), content (what the subject has a liberty to do), and object (the party with respect to whom the liberty is held). In order to construct a working explanatory model of defensive rights I propose to add to this schema a further element which we may call the end of the right. In the following discussion the end of a defensive right will be defined as the good or value which a defensive action is intended to preserve or protect.
The moral grounding of defensive rights may be visualized as a stool with three legs. Each leg of the explanation centres on a particular normative relationship between the elements associated with the right. The first leg concerns the relationship between the agent which possesses the right and the good which the defensive