International Law as a Belief System considers how we construct international legal discourses and the self-referentiality at the centre of all legal arguments about international law. It explores how the fundamental doctrines (e.g. sources, responsibility, statehood, personality, interpretation and jus cogens etc.) constrain legal reasoning by inventing their own origin and dictating the nature of their functioning. In this innovative work, d'Aspremont argues that these processes constitute the mark of a belief system. This book invites international lawyers to temporarily suspend some of their understandings about the fundamental doctrines they adhere to in their professional activities. It aims to provide readers with new tools to reinvent the thinking about international law and combines theory and practice to offer insights that are valuable for both theorists and practitioners.