Mistake and fairness: divergence of doctrines and room for harmonization

The three contract laws in the Greater Bay Area deal with vitiating factors such as mistake and fairness. The rules are different on what are the mistakes that would vitiate a contract: a common mistake or a unilateral mistake or the nature and type of the mistake. Neither can they identify if contract law should care about fairness; if so, what makes a contract unfair or what kind of unfairness is undesirable and warrants relief. Still, despite the visible divergence, using the insights of contract as voluntary commutative justice, whether one can escape contract for a mistake hinges upon whether it is fair economically for the non-mistaken party if the mistaken party were to escape the contract. To obtain relief for unfairness, economic unfairness is necessary, without which the contract would not be unfair despite the bargaining inequality.