This book critically examines the conception of legal science and the nature of law developed by Hans Kelsen. It provides a single, dedicated space for a range of established European scholars to engage with the influential work of this Austrian jurist, legal philosopher, and political philosopher.

Chapter 1: Introduction (Peter Langford, Ian Bryan and John McGarry).- Part I: Legal Science Before The Tribunal Of Validity.-Chapter 2: Hans Kelsen and the Social Fact Thesis (Lorenz Kähler).-Chapter 3: Natural Law and the Nature of Law: Kelsen's Paradox (Pierre-Yves Quiviger).- Part II: Beyond Natural Law?.- Chapter 4: Natural Law Systematics: Is There a 'Grundnorm' in Natural Law? (Claes Peterson).- Part III: Kelsen's Constitutionalism.- Chapter 5: Kelsen and Contemporary Constitutionalism: The Continued Presence of Kelsenian Themes (Paolo Carrozza).- Chapter 6: Constitutionalism and Value-Free Method: Kelsen's Legacy in Contemporary Challenges (Valeria Giordano).- Part IV: Against Practical Reason.- Chapter 7: Hans Kelsen and Practical Reason (Francesco Viola).- Chapter 8: Kelsen and Legal Interpretation (Isabelle Lifante).- Chapter 9: Validity and Correctness in Kelsen's Theory of Legal Interpretation (José Manuel Cabra).- Part V: Legal Science And Human Rights.- Chapter 10: HansKelsen's Works and the Modern Theories of Human Rights (Véronique Champeil-Desplats).- Chapter 11: Kelsen on Democracy in Light of Contemporary Theories of Human Rights (Christine Chwaszcza).- Chapter 12: Individual Sovereignty: From Kelsen to the Increase in the Sources of the Law (Francescomaria Tedesco).- Part VI: The Triumph Of Legal Science?.- Chapter 13: Kelsen and the Necessity of God in the Natural-Law Doctrine (John McGarry).- Chapter 14: Kelsen on Natural Law and Legal Science (Jan-Reinard Sieckmann).- Chapter 15: An Enduring Critical Affair: Kelsen and the Natural Law Tradition (Pierluigi Chaissoni).- Chapter 16: Conclusion: Positive Law and the Kelsenian Project (Peter Langford, Ian Bryan and John McGarry).