Contemporary contract theories fail to escape their bondage to 19th century liberal philosophers. Some are based on utility or preference satisfaction, but they disregard justice. Others try to extract conclusions for general concepts such as liberty or autonomy but they cannot do so without first smuggling their conclusions in the definitions of these concepts. These problems can be resolved by looking in a different direction: to the Aristotelian idea of contract as commutive justice on which contract theory was grounded before the 19th century. In the Aristotelian tradition, a contract of exchange was defined in terms of its purpose: to enable each party to obtain what he valued more in return for what he valued less without enriching the other party at his own expense. It united a concern for concept of a contract, the purposes of the parties, and the justice of their transaction rather than splitting them apart.