Palmer v. Donner was a United States Supreme Court case that dealt with the issue of a contract between two parties. The case involved a dispute between Palmer and Donner, who had entered into a contract for the sale of a parcel of land. Palmer had agreed to pay Donner $2,000 for the land, but Donner refused to accept the payment and instead demanded a higher price. The Supreme Court held that Donner was not entitled to a higher price than the one agreed upon in the contract. The Court reasoned that the contract was valid and binding, and that Donner was not entitled to a higher price than the one agreed upon. The Court also held that Palmer was entitled to damages for breach of contract, as Donner had refused to accept the payment. The Court's decision in Palmer v. Donner established the principle that a contract is binding and enforceable, and that a party cannot unilaterally change the terms of the contract. The decision also established the principle that a party who breaches a contract is liable for damages.

In the case of Palmer v. Donner, the Supreme Court was asked to decide whether a deed from one party to another could be voided due to fraud or mistake. The majority opinion held that such a deed should not be voided unless it can be proven that there was actual fraud in its execution. However, Justice Field dissented and argued that if it is shown that the parties were mistaken as to some material fact when executing the deed, then it should be voidable regardless of any fraudulent intent on either side. He reasoned that allowing mistakes in deeds would lead to greater fairness and justice for all involved parties since they would have an opportunity for relief even if no malicious intent had been present at the time of signing. Furthermore, he noted how this rule has long been accepted by courts across many states prior to this decision and thus urged his colleagues not overturn existing precedent without good cause.