The misconceived doctrine of causa and the incoherence of contemporary contract law

According to the doctrine of causa, there are two reasons (causae) why the parties would enter into an agreement and the law would enforce one: to get an equivalent in return for what one gave and to confer a benefit on the other party gratuitously. This doctrine, formulated on the basis of Aristotelian ideas of voluntary commutative justice and liberality, was accepted by civil law jurists through the 18th century. In the early 19th century, common law writers identified the first kind of causa with the consideration required in an action of assumpsit. The doctrine was incorporated in the French Civil Code of 1804. It ceased to make sense, however, because the idea of equality in exchange ceased to make sense. Anglo-American jurists defined consideration and French jurists defined causa or cause to exclude the idea of equality or fairness in exchange. Yet in both countries, the courts have applied these doctrines to give relief when an exchange was unfair. Although French legislation abolished the doctrine of cause in 2016, it preserved the results the court had reached. The recurring concern for fairness in exchange is evidence that one cannot do without the idea of contract of exchange as commutative justice. To understand contemporary contract law, we need to revisit the moral foundation that inspired causa, contract as voluntary commutative justice.