This text blends classic common law contract cases with 21st-century opinions and draws upon the problem method of instruction. It compares and contrasts the common law of contracts, the Restatement of the Law Second-Contracts, and Uniform Commercial Code Article 2 rules, as well as the United Nations Convention on Contracts for the International Sale of Goods and the UNIDROIT Principles of International Commercial Contracts, and explores their evolution and application. It emphasizes the importance of context to the application of legal principles and discusses the overlap between the knowledge and skills of a litigator and those of a transactional attorney.