Abstract

This article deals with the problem of justification of war in the light of Leibnizian natural right and deontic definitions. From an analysis of the principles of rationality on which, according to Leibniz, the justification of an act is based, it proposes “deontic types of war” - namely: justifiable wars (whether just or facultative), just wars (defensive war, war of cooperation), facultative wars (preventive war, humanitarian intervention), unjust wars (war of aggression, war of extermination, terrorism) -, which express the modality according to which their agents are constrained to act, namely: authorized, necessarily justified, contingently justified or unjustified to the military action. This modalisation is illustrated by a “war casuistry”, mostly taken from Leibniz’s reflections on the wars of his time. As it will be seen, our hypothesis states that the sufficient reason for a war is at bottom identified with the principle of the best, whose application requires an examination of the consequences of action in different possible scenarios.