The purpose of this thesis is theory development. It begins by evaluating existing explanations of why states undertake humanitarian intervention. Realists argue that states only intervene when their national interests are at stake. Normative scholars argue that states are at times motivated to save foreign citizens. Neither approach adequately accounts for the pattern of post-Cold War state practice. Building from this conclusion, the thesis conducts research based on two propositions derived from an analysis of existing debates: that examining state motive holds promise for elucidating the weaknesses in current approaches and that studying state argumentation can provide insight into state motives. To better investigate state motives, a theoretical framework is developed to explain how motives translate into state decision-making and manifest themselves in state argumentation. By employing process tracing, argumentation analysis, and elite interviews, this framework is applied to three cases: Northern Iraq in 1991, Rwanda in 1994, and East Timor in 1999. Each case study constructs a theoretically informed narrative, assesses debates between states at the United Nations Security Council, and evaluates the consistency between state discourse and state practice. The cases are then used heuristically to identify opportunities for improving existing theory and developing new theory. This yields several conclusions. First, not only do states often possess mixed motives, but the humanitarian impulse also appears in some cases to have been a necessary condition for humanitarian intervention. Second, the norm of humanitarian intervention does not function as a general rule. Rather, it is a cluster of principles derived from just war theory and international law, but also connected to related norms about sovereignty, human rights, and self-determination. Third, state decision-making is a collective process structured by the prevailing post-Cold War institutional and normative context. The thesis concludes by outlining promising avenues of research for better understanding why states respond to some occurrences of mass atrocities and not others.

La lutte contre l’impunité telle qu’elle est menée par la Cour pénale internationale est critiquée et suscite la controverse. Les actions de l’institution pénale internationale sont perçues par ses critiques comme reconduisant des formes de racisme, d’ethnocentrisme, d’impérialisme, de néocolonialisme, d’autoritarisme qui corrompent fondamentalement l’aspiration à la justice. Paradoxalement, le besoin d’une justice pénale internationale s’entend comme un impératif de paix et de justice. Ce mémoire questionne et examine les justifications d’un tel impératif moral. Il part de l’hypothèse que celui-ci est catégorique et relève d’une approche éthique déontologique. Les justifications d’une telle hypothèse découlent d’une analyse des différents contextes historiques ayant vus l’affirmation ou les ré-affirmations d’un rejet catégorique des crimes d’inhumanité (article 5 du Statut de Rome de la Cour pénale internationale : le crime de génocide, les crimes contre l’humanité, les crimes de guerre, les crimes d’agression). Ces condamnations ont posé les bases d’une éthique de portée universelle et ont reconnu en l’humanité une communauté morale universelle. Ainsi, indifféremment des particularismes moraux et éthiques, les fondements philosophiques de la lutte contre l’impunité reposent sur un universalisme moral et l’idée régulatrice d’un contrat éthique liant la communauté des États et des peuples. Il est question d’être et de faire humanité. Dès lors, en dépit; des théories réalistes en relations internationales suggérant à la fois l’amoralité des relations inter-étatiques, des motivations prudentielles et de la rationalité instrumentale (moralité de l’intérêt), en dépit des perspectives culturalistes qui témoignent d’un pluralisme moral et éthique, nous voulons démontrer que la lutte contre l’impunité est avant tout un devoir moral universalisable (fondé sur le principe de dignité) de nature déontologique (même si cette lutte implique aussi des considérations conséquentialistes). Face à la complexité de cette problématique, notre recherche sera transdisciplinaire; et notre approche combine et le déductivisme. / The fight against impunity as conducted by the International Criminal Court is criticized and controversial. The actions of the international criminal institution are perceived by its critics as renewing forms of racism, ethnocentrism, imperialism, neocolonialism, authoritarianism that fundamentally corrupt the aspiration to justice. Paradoxically, the need for international criminal justice is understood as an imperative of peace and justice. This research examines the justifications for such a moral imperative. It starts from the assumption that it is categorical and comes from an ethical approach to ethics. The justifications for such an assumption rest analysis of the different historical contexts that have seen the affirmation or re-affirmation of a categorical rejection of crimes of inhumanity (Article 5 of the Rome Statute of the International Criminal Court: the crime of genocide, crimes against humanity, war crimes, crimes of aggression). These condemnations laid the foundations for an ethic of universal significance and recognized humanity as a universal moral community. Thus, despite moral and ethical particularisms, the philosophical foundations of the fight against impunity is based on a moral universalism and the regulating idea of an ethical contract linking the community of states and peoples. It is about being and making humanity. Therefore, in spite of; realistic theories of international relations suggesting both the amorality of inter-state relations, prudential motivations and instrumental rationality (morality of interest), despite the culturalist perspectives that testify to moral and ethical pluralism, we want to show that the fight against impunity is above all an universalizable moral duty (based on the principle of dignity) of a deontological nature (even if this struggle also implies consequentialist considerations). Given the complexity of this issue, our research will be transdisciplinary; and our approach combines inductivism and deductivism.