Legitimacy, when challenged, bases itself on an appeal to the past, whilst justification relates to an end that lies in the future. Violence can be justifiable, but it never will be legitimate.
The implication of Hannah Arendt's well-known distinction is that legitimate action must claim to conform to a pre-existent normative code; justification, on the other hand, is based on the action's results, seen as serving some higher aim or objective. Her wider argument is, of co urse, that the consequentialist calculus that may justify individual acts of violence can never obliterate their fundamental moral deficiency. For Arendt, carrying out the lesser or necessary evil is never legitimate (i.e., it never conforms to her implied notion of a pre-existence, fundamental normative code), because for her, a truly rational moral code could never describe violence as something good or just. It may be justified (or, more circumspectly justifiable), but this categorisation is always short term and results driven; it sets no precedent and it has no ‘appeal to the past’ for validation. Even in the face of a great moral evil, an act of violence can, for Arendt, never be purely good. Arendt's contribution is a recent instalment in a longer history of the ethical evaluation of violence. In European thought, these divisions, in part at least, created the twin disciplines of law and politics. The distinctions she draws between justifiable contraventions of a moral code and allowable exceptions to the law would, however, be quite familiar to the ethical discussions of medieval Muslim authors. They are mirrored, to an extent, in the difference between shar’ (divine law) and siyāsa (pragmatic requirements of governance) in medieval Muslim discourse, where the term siyāsa brackets extra-legal (non-shar’) actions, justified primarily on consequentialist grounds. That is, they bring benefits to the community, and these must sometimes overrule the (apparent) requirements of the shar‘. It is important to remember, in contrast to Arendt's framework, violent acts can be found in both shar’ and siyāsa categories, and hence they may be (using her terms) legitimate or justifiable (or indeed both).
This book consists of a series of studies about violent acts in Muslim contexts, whether they were carried out by Muslims or by others, whether they are postulated or actual, whether they have happened, are happening currently or they may take place in the future.