Supermajority law might be defined as a constitutionally prescribed subcategory of laws with a quasi-constitutional character, which covers, at least theoretically, the most crucial legislative fields and is subject to stricter procedural safeguards than the requirements of the ordinary legislative process. This definition identifies three main distinctive features of supermajority law: its special rank within the hierarchy of legal norms, somewhere between the constitution and ordinary laws; its stricter procedure of enactment vis-à-vis the ordinary legislative process; and its constitutionally prescribed scope of application, focusing at least in principle on the most crucial legislative fields. The first chapter of the volume outlines the basic concept of supermajority law and the paramount constitutional concerns surrounding it. For this purpose, first, the aforementioned definition is detailed; then, the main questions and hypotheses of the book are presented. The methodology section describes the four main steps of the research: selecting constitutions that operate with supermajority law; comparing various supermajority law models around the world; assessing the five potential justifying arguments behind supermajority law; and formulating the proposed alternative model of this constitutional instrument. Although this book falls primarily in the field of constitutional law, the complex analysis of supermajority law requires the meaningful involvement of several other scientific disciplines. Therefore, this chapter also explores the role of political science, decision-making theory, and sociology in tackling the constitutional challenges raised by the introduction of supermajority law. Besides this, constitutional instruments classified under the category of supermajority law are mentioned under different denominations by national constitutions, which may cause considerable confusion. This chapter reflects this with a separate section devoted to various denominations of supermajority law, clarifying the terminological issues.