The concept of good faith as it pertains to Western contract law has existed since the Roman Republic. As a preeminent roman legal scholar, Cicero wrote: ‘Ut inter benos bene agier oportet et sine fraudatione’ – one must act well, as among good men without fraudulence. The Roman law recognized the concept of bona fides and most western civilizations have developed legal systems that require some degree of good faith between contracting parties. For the Roman lawyer, good faith or bona fide meant fidelity to promise. At common law it asks what a reasonable person would take the parties to have meant at the time of their agreement. Civil law nations such as Germany have codified the obligation of good faith, as has the United States in its Uniform Commercial Code, but its concept of good faith is not as extensive as its civil law peers. The UK has not formally codified good faith, but it has been recognized in many judicial decisions. Additionally, all of the above-mentioned countries are at least signatories to the United Nations Convention on Contracts for the International Sale of Goods (CISG) , and the International Institute for the Unification of Private Law (UNIDROIT), which both mandate that parties contract in good faith. But while good faith is at least recognized by these countries, it has not been implemented even handedly. History has altered good faith, and it has evolved to suit the needs of the cultures that have adopted it. This paper seeks to explore the transmission of the concept of good faith from Roman law to common law, from civilian to case law systems.
Martin, Samuel, The Evolution of Good Faith in Western Contract Law (May 12, 2018).