Thackrah v. Haas 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 Thackrah and Haas, in which Thackrah agreed to pay Haas a certain amount of money for the use of a patent. Thackrah failed to pay the amount due, and Haas sued for breach of contract. The Supreme Court held that the contract between Thackrah and Haas 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 other's promise. The Court also found that the contract was not void for lack of consideration, as Thackrah had promised to pay a certain amount of money for the use of the patent. The Court also held that the contract was not void for lack of mutuality of obligation, as both parties had promised to do something in exchange for the other's promise. The Court found that the contract was valid and enforceable, and that Haas was entitled to recover the amount due under the contract. In conclusion, the Supreme Court held that the contract between Thackrah and Haas was valid and enforceable, and that Haas was entitled to recover the amount due under the contract. The Court's decision established that contracts must be supported by consideration and mutuality of obligation in order to be valid and enforceable.

Justice Field delivered the dissenting opinion in Thackrah v. Haas, arguing that the lower court's decision should be reversed and judgment entered for the plaintiff. He argued that under California law, a contract of sale was formed when an offer to purchase goods was accepted by delivery of those goods with payment to follow at a later date. In this case, he noted that there had been an agreement between the parties whereby Haas agreed to deliver certain merchandise on credit and Thackrah agreed to pay for it within sixty days after receipt of invoice or statement from Haas. The fact that no written memorandum existed did not invalidate their agreement as long as both parties understood its terms and conditions; thus, Justice Field concluded that since all elements necessary for a valid contract were present here - mutual assent, consideration (the promise by each party), subject matter (the merchandise) - then such an oral contract could be enforced against either party who failed to fulfill his obligations under it.