This chapter introduces the concepts of obligation and contract. It defines obligation as a legal or moral duty and notes there is no single definition. Contract is defined as a legally enforceable promise or agreement. The key elements of a valid contract are identified as capacity, consent, object, and form if required. Sources of obligations are contractual, from terms of a contract, and non-contractual from other legal sources like tort. Historical development saw contract law emerge in the 19th century from commercial disputes in a period of expanding trade.