This chapter defines the core subject and methodology of the Common Theory of Law, positioning it as both a legal and social science that investigates the universal patterns, origins, and evolution of legal phenomena. It explains the discipline’s role in identifying the systemic nature of law within society, distinct from narrower sectoral legal sciences. The chapter outlines its essential functions—cognitive, heuristic, and prognostic—and details the methodological principles that guide its research, including historicism, objectivity, concreteness, and pluralism. Logical tools such as induction, deduction, synthesis, and hypothesis formulation are highlighted as mechanisms for scientific inquiry and theory building. Furthermore, the chapter explores the Common Theory’s integrative function within the legal sciences, providing the conceptual foundation for both theoretical-historical and sectoral disciplines. Finally, it critically evaluates the challenges in legal education across post-Soviet states, especially the lingering dominance of statist-positivist frameworks. It calls for a shift toward value-based, pluralistic, and interdisciplinary teaching to build a healthier legal culture and promote critical engagement with legal theory.