Harkness v. Hyde was a United States Supreme Court case that dealt with the issue of whether a contract between two parties was valid. The case involved a contract between the plaintiff, Harkness, and the defendant, Hyde, in which Hyde agreed to pay Harkness a certain sum of money in exchange for Harkness's services. Harkness argued that the contract was valid and enforceable, while Hyde argued that the contract was invalid because it was not in writing. The Supreme Court held that the contract was valid and enforceable. The Court reasoned that the contract was valid because it was supported by consideration, meaning that both parties had given something of value in exchange for the other's promise. The Court also noted that the contract was supported by the parties' conduct, as Hyde had paid Harkness a portion of the money he had promised. The Court concluded that the contract was valid and enforceable, and that Harkness was entitled to the remaining money that Hyde had promised.

Justice Field delivered the dissenting opinion in Harkness v. Hyde, arguing that the court should not have reversed a decision of the Supreme Court of California. He argued that it was inappropriate for the federal courts to interfere with state decisions unless there had been an abuse or violation of some right secured by national law or treaty. In this case, he did not believe such interference was necessary because no constitutional rights were violated and no federal laws were broken; rather, it appeared to be a dispute over property rights between two private parties which could be resolved through existing state laws and procedures. Furthermore, Justice Field noted that even if there had been some error in interpreting state law on behalf of one party or another, this would still not justify overturning a decision made by a competent tribunal within its own jurisdiction - especially when doing so would create uncertainty about how similar cases should be decided in future proceedings.