Good v. Martin was a United States Supreme Court case that dealt with the issue of whether a contract between two parties was valid. The case involved two parties, Good and Martin, who had entered into a contract for the sale of a piece of land. Good had agreed to pay Martin $1,000 for the land, but Martin refused to accept the payment and instead demanded $2,000. Good then sued Martin for breach of contract. The Supreme Court held that the contract between Good and Martin was valid and enforceable. The Court found that the contract was supported by consideration, meaning that both parties had given something of value in exchange for the land. The Court also found that the contract was not unconscionable, meaning that it was not so one-sided as to be unfair. The Court ultimately held that Martin was obligated to accept the $1,000 payment from Good and that Good was entitled to the land. The Court also held that Martin was liable for damages for breach of contract. This case established the principle that contracts are binding and enforceable, and that parties must abide by the terms of the contract.

Justice Field delivered the dissenting opinion in Good v. Martin, arguing that the majority's decision was contrary to established precedent and would lead to confusion among lower courts. He argued that a contract between two parties should be enforced as written unless it is against public policy or otherwise illegal. In this case, he noted that there was no evidence of fraud or illegality on either side; thus, both parties had agreed to certain terms which should have been upheld by the court. Furthermore, Justice Field argued that if one party could unilaterally change an agreement after it had already been signed without any legal justification for doing so then contracts would become meaningless and unenforceable in court. Finally, he concluded by noting that while equity may sometimes require modification of a contract due to unforeseen circumstances such modifications must still be within reasonable limits set forth by law and not based solely upon one party's unilateral wishes.