The series in which this book appears is Cambridge Introductions to Philosophy and Law. There is a special challenge to philosophical introductions to law – in particular, when the topic to be introduced “philosophically” is a doctrinal area of law. It is difficult to speak knowledgeably about the theoretical aspects of contract law in general, or about particular subcategories (doctrinal rules and principles, or transaction types), without a strong grounding in the specific rules and cases. For that reason, this book offers an introduction to philosophy and contract law that is grounded on the detailed rules and principles of American contract law; the book then offers theoretical claims that can be made regarding those rules and principles. As will be seen, such claims can be made at different levels: the individual rules, “doctrine,” transaction types, and American contract law more generally. It will be part of the theoretical argument of Chapters 8 and 9 that particular claims about the nature of (American) contract law, and claims one level of abstraction up, about the nature of contract theorizing, are weakened or refuted by the details of existing contract law rules. The theoretical discussions in this book are most present in Chapters 1, 8, and 9, and in end sections of other chapters; the historical discussions are primarily in Chapter 2 and one section of Chapter 3; there are doctrinal discussions throughout.

It is also part of the view underlying this text that theories of an area of law need to be supported by, or at least informed by, history. Understanding contract law is in part a process of understanding why we have the rules and principles we have. Too often in law schools, law journals, and elsewhere, discussions of the purpose of contract doctrine (and doctrine from other areas of law) are a strange form of “just so” story known as “rational reconstruction” – what justification could be offered for the rules we actually have, regardless of whether that justification has any connection to the actual reasons for why the rule was introduced or why it persisted.