Introduction: Is Practical Reason Unitary or Fragmentary?And Why Should Jurisprudence Care?

This text serves as the introduction to the book Law and the Unity of Practical Reasoning (Hart Publishing, Oxford, 2025). Written by the four co-editors of the volume, it is divided into four main sections. The first section, “Reason, Reasons, Reasoning,” is devoted to presenting the distinctions between these concepts. The second section, “Unity and Fragmentation: Epistemic and Practical,” discusses the various grounds for distinguishing between epistemic and practical reasons, as well as the conceptions that support either the unity or fragmentation of practical reasoning in this regard. The third section, “Unity and Fragmentation: Practical Reason,” introduces the specific debate about the unity or fragmentation of reasons and reasoning within the practical domain. The fourth and final section, “Law and the Unity/Fragmentation Debate,” explicitly connects the book’s central topic with reflections on whether law constitutes reasons for action. In particular, it explores how different theses concerning the unity and fragmentation of practical reason affect the interpretation of law, its capacity to justify decisions, and the idea of legal authority.