 Canonist substantive fairness shifted to procedural fairness, so good faith and mutual assent were retained as requirements, but just price and "laesio enormis" were not.Under English rule, public policy was substituted for "bonos mores".Initially under Roman-Dutch law the broad notion of "iusta causa" was necessary to create obligations; therefore, for a contract to be enforceable, it had to be shown to be based on a "causa".