Book excerpt: Foundations of Private Law is a treatise on the Western law of property, contract, tort and unjust enrichment in both common law systems and civil law systems. The thesis of the book is that underlying these fields of law are common principles, and that these principles can be used to explain the history and development of these areas. These underlying common principles are matters of common sense, which were given their archetypal expression by older jurists who wrote in the Aristotelian tradition. These principles shaped the development of Western law but can resolve legal problems which these older writers did not confront.