3. Most of the general principles of the modern English law of contract were developed and elaborated in the eighteenth and nineteenth centuries. To the judges of the eighteenth century the philosophy of laissez-faire combined with the theories of natural law meant that men had an inalienable right to own property, and hence to make their own arrangements to buy or sell or otherwise deal with that property, and hence to make their own contracts. This largely meant that the law of contract was designed to provide for the enforcement of private arrangements which the contracting parties had agreed upon. In general the law was not concerned either with the fairness or justice of the outcome, nor with the possibility that the contract might not be in the "public interest." The idea of "freedom of contract" (1) emphasized that contracts were based upon mutual agreement, and (2) it stressed that the creation of a contract was the result of free choice unhampered by external control. It is doubtful if either of these two ideas was ever completely valid, and by the late nineteenth century changes in social and economic conditions and in the practice of the courts already indicated that freedom of contract was becoming very different from what was claimed. The development of the law was being influenced by an emphasis on an objective approach to questions of agreement and the intention of the parties. Thus, the law of contract was becoming encumbered by more complicated rules making it more difficult to identify the intention of the parties. An illustration of this tendency is the doctrine of impossibility (or frustration) which permits a contract to be dissolved or voided if it becomes impossible to perform because of some extraordinary event occurring without either parties fault.

Why would it be in the joint interests of the contracting parties to have their contractual arrangements constrained by the doctrine of impossibility, and thus limit freedom of contract? The doctrine of mutual mistake is also considered to be a "fairness doctrine" along with impossibility. Explain why voiding contracts that involve mutual mistake would contribute to forming socially efficient contractual arrangements. That is, what is the source of social gain from these doctrines?