In Arthur v. Lahey, the Supreme Court of the United States was asked to decide whether a contract between two parties was valid. The contract in question was between Arthur and Lahey, and it stated that Arthur would pay Lahey a certain amount of money in exchange for Lahey's promise to convey certain real estate to Arthur. The Supreme Court held that the contract was valid and enforceable. The Court noted that the contract was clear and unambiguous, and that the parties had agreed to its terms. Furthermore, the Court found that the consideration for the contract was sufficient, as Arthur had paid Lahey the agreed-upon amount of money. The Court also held that the contract was not voidable due to any lack of capacity on the part of either party. The Court noted that both parties were of sound mind and had the capacity to enter into a contract. In conclusion, the Supreme Court held that the contract between Arthur and Lahey was valid and enforceable.

In Arthur v. Lahey, the Supreme Court was asked to decide whether a contract between two parties that had been partially performed could be enforced by one of them against the other. The majority opinion held that it could not, as there was no consideration for such an agreement and thus it did not meet the requirements of a valid contract under common law. However, in his dissent Justice Field argued that while contracts without consideration are generally unenforceable, this case should be treated differently because both parties had already acted on their agreement and were relying upon each other's performance when they entered into it. He further noted that if one party is allowed to back out after having received some benefit from another's performance then all agreements would become uncertain and unreliable which would ultimately harm commerce and society at large. Therefore he concluded that even though there may have been no initial consideration given for this particular contract, its partial execution should suffice as sufficient evidence of mutual reliance between the two parties so as to make it enforceable in court.