This innovative and thought-provoking book studies how subrogation and marshalling should be understood in the context of private law. Subrogation and marshalling are legal rules which give a person new rights with prima facie the same content as someone else's extinguished rights. There is little examination of why the law does this. This book argues that the key to understanding subrogation is the distinctive form of the rights that it creates. The form of rights created reflects a particular role in ensuring interpersonal justice: subrogation's role is to properly distribute the burden of debts. Taking this model, the book goes on to resolve persistent controversies in the case law, including when subrogation should occur, what rights it should create, the relationship between subrogation and marshalling, and whether subrogation is a remedy for unjust enrichment.