This comprehensive book provides a comparative overview of legal institutions that intersect with everyday life: contracts, unilateral legal transactions, torts, negotiorum gestio and unjust enrichment. These institutions form the core of the Law of Obligations, which is examined in this book from the perspective of all major legal traditions including Civil, Common, Islamic and Chinese law. Offering a critical understanding of the legal regulation of institutions in national legal systems, the book identifies distinct concepts of the law of obligations that emerge from them and explains their underlying motives. The author provides valuable insights into how differently basic legal institutions are regulated across national borders, as well as unveiling the roots of legal institutions of the utmost significance in international trade such as contracts, pre-contractual liability, liability for torts and restitution of unjust enrichment. This book will be a helpful resource for academics and practitioners involved in international litigation and arbitration proceedings concerning contracts, torts and other sources of obligations.