If, in making a contract it is taken for granted by both parties that a certain fact exists, which, if not existing, would make the contract impossible of execution, the contract is void. Thus, in contracts for the sale of specific personal property, its existence at the time of the sale is generally assumed. If the property has perished or been destroyed, the contract is void. The same rule has been applied to the sale of non-existent reality, of the transfer of void or spurious securities, of the assignment of a void lease. In all these cases the money paid in misreliance on the void contract is recoverable.

Premiums paid on a policy of marine insurance by one who in reality had no goods on board, or for a voyage that was never begun, may be recovered. The existence of a risk is assumed by both parties, in fact there is no risk, consequently there was nothing to which the contract of insurance related.

"A promise," says Woodward, "which is so general or indefinite that it does not enable the courts to determine the nature and extent of the obligation assumed must be regarded as no promise at all. Such has been the fate of a promise to pay good wages; a promise to convey a hundred acres of land, the land not being described; a promise to divide profits, no rate of division being indicated. Instances might be multiplied. A benefit conferred, in the honest, though mistaken, belief that such a promise is binding ought in justice to be restored. Restitution is accordingly enforced."

The law requires some kinds of contracts to be executed in a particular manner. Thus, by statute, many municipalities can make contracts, or those of a particular kind, only on sealed bids or proposals and after proper advertising for bids, etc. If these things are not done, the contract made in disregard of them is invalid. The courts of this country have got into deep confusion in applying this rule to private corporations. Suppose a corporation makes a loan without proper authority and receives the money, can the lender recover it? The corporation had no right to borrow, of this the lender knew as well as the borrower. Both parties are in the wrong. The highest court in this country has been more consistent than many of the state courts, and holds that a contract it cannot make for lack of legal power is not made and cannot be ratified. "No performance on either side can give the unlawful contract any validity, or be the foundation of any right of action upon it." Nevertheless though a contract is unlawful and void because the corporation was unable to make it, a court strives to do justice between the parties by permitting property or money, parted with on faith of the unlawful contract, to be recovered back, or compensation to be made therefor.

The lack of another legal requirement in making contracts gives rise to serious consequences. We have learned that the Statute of Frauds requires for the validity of many contracts that a memorandum of them be made in writing and signed by one or both contracting parties. By English law the statute provides a rule of evidence, that a writing must be shown as proof of a contract before the courts will consider it as having been made; by some of the American courts a contract that does not meet the requirements of the statute is held to be void; by other courts they declare that though the contract is not void it cannot be enforced.

While the Statute of Frauds in some states is regarded as completely nullifying contracts not conforming to its requirements, they are not anywhere held to be illegal, that is, are not made in violation of law. "There appears," says Woodward, "to be no reason of policy, therefore, for denying to a party thereto in a proper case, the aid of the court in obtaining quasi contractual relief, or the right to establish the justice of his quasi contractual demand by proving the terms of the unenforceable agreement. True, the evidence of the agreement in such a case, must be oral; but since the evidence is for the purpose of proving, not a contract as such, but a transaction resulting in an unjust benefit to the defendant, its introduction would seem not to contravene the statute."

A purchaser of land under an oral contract, who is given possession and subsequently fails to pay, is liable for the use of the land to him while he has occupied it. Though the act of the seller in giving the purchaser possession without conveying the title may not be regarded as a part performance of the contract of sale, yet the benefit resulting to the purchaser creates an obligation to make restitution which the courts will enforce. The improvement of land by the purchaser under an oral contract is an act which enables him to enforce the contract in equity. Improvements made by a lessee under an oral lease within the statute are governed by the same rules as those of improvements made by a purchaser.

If no benefit has been derived from the contract, nothing can be recovered. Thus, a son worked for his father on his father's farm under an unenforceable contract with his uncle. The latter was under no quasi contractual obligation to pay the value of such service, since he had derived no benefit from them. Likewise one who, relying on an unenforceable contract, constructed a wood-chopping machine that was not accepted could not recover for the value of his labor and materials.

Again, where one party by his own act or default has prevented the other party from fully performing his contract, the party thus preventing performance cannot take advantage of his own act or default, and screen himself from payment for what has been done under the contract. Thus, if one party agrees with another to work on a house the law implies that the employee owns the building in which the work is to be done. This is a part of the contract whether the house is clearly specified or not. Therefore, an employer who does not own the house, or parts with it before the work is completed, is liable to the other party.

The destruction of a thing in the course of alteration or repair without the fault of the bailee is a case like that above mentioned. The labor and materials are expended in response to the desire of the owner of the property, and therefore it is just that he should pay for the property he destroyed. In one of the old cases a horse was sent to a farrier to be cured and was burnt before a cure was completely effected. Nevertheless, the farrier was entitled to payment for what he had done. Likewise, the owner of a ship that is destroyed by fire a few hours before the completion of repairs, cannot escape payment on the ground that he has reaped no advantage.