In the Volokh conspiracy blog, the question about marriage being a contract is asked.
He responded “I thought I’d respond to this on-blog because it illustrates a considerably broader point: In law, as in life, concepts like “contract” aren’t unitary things, so that either something is a contract and has all the properties of a contract or something isn’t a contract. There are different kinds of contract, with different qualities, and different possible definitions for the term “contract.”
To begin with, “contract” is a quite broad concept. I don’t want to try to give a thorough definition here, but suffice it to say that an exchange of promises might well be a contract even if the promises don’t involve money, goods, or even services. Thus, for instance, “Each of us promises not to be anyone else’s bridge partner” can be a contract; it’s an exchange of promises not to engage in certain conduct. (Note that the contract doesn’t promise that I’ll be your bridge partner, just that I won’t be anyone else’s.) Substitute something else for “bridge,” and you’ll have one aspect of a marriage contract.
But beyond this, it turns out that a marriage contract is a contract — it’s an exchange of promises, it has effect because of consent of the parties, and it after all is called a marriage “contract.” But it also has many consequences that a normal contract doesn’t have: Not so long ago, it turned otherwise criminal sexual conduct (fornication) into legal conduct. Even today, it has that effect with marriages where one party is too young to consent to sex but old enough to consent to marriage (usually with the parents’ consent). It makes the parties’ children legitimate, which used to have very important legal effects and still has some legal effects. It gives the parties the right to refuse to testify against each other in court. If one party is not a citizen, it gives the party a relatively easy path to citizenship. The list could go on.
It also lacks some of the properties of a normal contract. It can be severed pursuant to divorce laws without the opportunity to sue for damages for breach of contract. It is not governed by the Contracts Clause of the Constitution, so that newly enacted divorce laws could impair the obligation of existing contracts of marriage (see the Dartmouth College Case (1819)).
So marriage is a contract, and has long been described as a contract, but it’s a very peculiar kind of contract that has its own special legal rules. To ask whether marriage is “technically” a contract doesn’t make much sense, because it presupposes a single unique meaning for the term “contract.” If by contract you mean “a contract as typically defined at law,” which is to say a contract that has most of the legal consequences that a typical contract has, then the answer is “largely not,” because marriage contracts have such specialized legal consequences. If by contract you mean “something the law has typically labeled a contract,” the answer is “probably yes,” simply because “marriage contract” has long been a common term. If by contract you mean “a mutual agreement that the law treats as binding as a consequence of the parties’ having agreed to it,” then the answer is “yes.”
So, as I said, there are different kinds of contract, with different qualities, and different possible definitions for the term “contract.” In math, you can ask, “is a number even, or is it odd?” In law, asking “is X a contract?” will often yield the response, “in what sense, and for what purposes?”