Within this model the relationship between the two parties is an exclusive one. It is characterised by the consideration flowing from the promisee. The consideration given is the payment for the price of the promise. As a third party has not provided consideration, and paid no price .

             for the promise, it would possibly be unjust if he or she were able to intervene, (suing on the contract) conceivably invading the autonomy of the in personum relationship of the parties involved. In appointing a right in a two-party contract only to the parties involved, the law of contract is about private justice as it protects the autonomy of the parties, leaving them less exposed to potential liability from non-parties who have not provided consideration.

             The law of contract is also about private justice when treating third parties as 'parties to a contract," and moreover, private injustice. In Trident, private injustice is a crucial element of the 'radical" argument in the debate concerning privity of contract. .

             The radicals emphasise that a cause of action should be allowed in contract for McNeice, as Trident made a contract to insure "Blue Circle Southern Cement Limited, all its subsidiary, associated and related Companies, all Contractors and Sub-Contractors and/or Suppliers."3 Mason CJ and Wilson J agreed that this policy was "intended to cover any contractor, sub-contractor or supplier"4 (hence McNeice). And while they ponder the "problems arising"5 from allowing a third party a cause of action on promise, they consider the "injustice which flows from a.failure to give effect to expressed intention."6 and the 'private injustice" of contract law that would flow from this failure. .

             The combination of private justice, and public regulation is given rise to by the very nature of contract law. In a large societies social sanctions are largely ineffective and so contract law adopts the role of public regulation by both enforcing contracts and reconciling breaches or discrepancies.