Arthur v. Homer is a United States Supreme Court case that was decided in 1877. The case involved a dispute between two parties over a contract for the sale of a horse. The plaintiff, Arthur, alleged that the defendant, Homer, had agreed to purchase a horse from him for a certain price. Arthur claimed that Homer had failed to pay the agreed-upon price and was thus in breach of contract. The Supreme Court held that Homer was liable for breach of contract. The Court found that Homer had agreed to purchase the horse from Arthur and had failed to pay the agreed-upon price. The Court also found that Arthur had performed his part of the contract by delivering the horse to Homer. Therefore, the Court held that Homer was liable for breach of contract and ordered him to pay the agreed-upon price to Arthur. The decision in Arthur v. Homer established that a party who fails to fulfill their contractual obligations is liable for breach of contract. This case is still cited today as an example of the legal principle that a party who fails to fulfill their contractual obligations is liable for breach of contract.

In the case of Arthur v. Homer, the Supreme Court was asked to decide whether a deed from one party to another is valid when it is not signed by both parties. The majority opinion held that such a deed was invalid and could not be enforced in court. However, Justice Field dissented from this decision, arguing that while it may have been customary for deeds to be signed by both parties at the time of execution, there were no laws or regulations requiring them to do so. He argued that if two people agreed on terms and conditions regarding property ownership then they should be allowed to enter into an enforceable contract without having their signatures affixed thereto. Furthermore, he noted that even though custom dictated otherwise at the time of this case's ruling, modern law had since changed and now accepted contracts with only one signature as being legally binding agreements between two parties.