The doctrine of relativity of title, i. e. the idea that every possessor has a property right enforceable against everyone except the true owner, is a core principle of property law in the common law tradition. It also exists in the civilian tradition, albeit with a much narrower scope. Felix Kiefner examines the doctrine of relativity of title in both traditions including its historical development, its shape in modern English and German law, the value judgements underlying the doctrine in different cases of possessors, and the extent of its explanatory power.