There is no consensus as to what the purpose of marriage is. But whatever its purpose, it is political. Private friendships, romances, sexual partners, economic alliances, housemates and other relationships are sometimes subject to legal agreements of lease and contract. But more often they are informal and mutually beneficial arrangements. Marriage is all these relationships made public and explicit. It benefits from social recognition and acceptance in return for public accountability in ways that previously private (and often implicit) vows of commitment that create new families do not.
Marriage is how society — or its body of political representatives — controls the reproduction of society: who can legitimately rear children and inherit property. The state traditionally subsidizes favourable families and de-legitimizes (and sometimes criminalizes) unfavourable forms based on age, ethnicity, gender, consanguinity, number of spouses, or whatever other criteria creeps into the imagination of the masses and our masters as constituting a proper or “natural” union.
The twentieth century saw the end of so-called miscegenation laws; laws which were the result of a confused project to restrict the reproduction of American society based on ethnicity and skin color. For those who see through the distorted logic of racism, there remains no comprehensible reason to exclude families from social recognition based on arbitrary notions of “race” that too often grab hold of humanity’s haunted mind. Likewise it is no easy task for many of us to understand those who currently wish to restrict marriage based on gender.
President Obama recently evoked his Christianity in prompting his change of heart about same-sex marriage. Others have been known to appeal to Christianity to argue against same-sex marriage. In his 2003 argument for privatizing marriage, one commentator wrote of the gay marriage debate, “It’s going to get ugly. And then it’s going to get boring.” Well, it’s gotten boring. Nay, beyond boring, it’s gotten frustratingly monotonous watching marginalized groups clamor for acceptance from their oppressors while all sides explain what Jesus would do.
I can think of one vaguely philosophic, though not very compelling, argument against abstract homosexuality. That is an argument from teleology: since men and women are endowed with some complementary bits, they are naturally meant to pair off. That argument not only assumes a binary gender, but to apply it to marriage is to presuppose that the sole purpose of marriage is sex and biological reproduction. Nobody takes that position. Despite those apparent weaknesses, Jesus does use such a teleological argument against divorce in the accounts of Matthew and Mark:
Some Pharisees came to him to test him. They asked, “Is it lawful for a man to divorce his wife for any and every reason?”
“Haven’t you read,” he replied, “that at the beginning the Creator ‘made them male and female,’ and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh’? So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate.” (Matthew 19:3-6)
One great thing about Jesus’ responses to the Pharisees is that he often confounds them by intentionally quoting passages of the Old Testament out of context (there’s a lesson there about sacralizing a book). In Genesis (2:24), which Jesus is quoting, the reason men and women are compelled to unite as ‘one flesh’ is because Woman was originally made from Adam’s rib. It’s an explanation for marriage—or at least for sexual union. Jesus divorces (pun!) the explanation (the rib story) from the result (the drive to sexual union) and substitutes the less etiological gender binary of Genesis 1:27 (‘male and female He created them’) as an explanation.
In Genesis 2, God separates Woman from Adam, and later men and women rejoin themselves in sexual union. In Matthew 19, Jesus ignores the mythology and reverses this story: “Therefore what God has joined together, let no one separate.” Now it is God doing the joining and people doing the separating. I’ll give my high-level interpretation: Men and women are attracted to each other not because of some imaginative creation myth, but because that is the nature of mammals with their sexuality and whatnot. Society will reproduce itself both biologically and culturally. — “Life finds a way,” as one chaos theorist put it. Even well-meaning attempts at regulating reproduction by establishing legal institutions to control who can legitimately begin or dissolve a family aren’t a part of Jesus’ vision of society.
As usual the Pharisees don’t quite catch that Jesus just reversed their assumptions and they continue their line of legal questioning: “Oh yeah, smart guy? If God did not intend divorce, then why did Moses allow it?” (Matthew 19:7). Jesus responds the same way he did in the Sermon on the Mount, by replacing law with morality. Moses told you not to murder; I tell you not to be angry. Moses told you not to commit adultery; I tell you not to lust. Moses told you to keep your oaths; I tell you not to make oaths, simply say ‘yes’ or ‘no’. Moses said an eye for an eye; I say give to those who steal from you. Moses said love your neighbor; I say love your enemy. Moses told you to be civilized about divorce; I tell you that divorce is tantamount to adultery (compare Matt. 5:31 and Matt. 19:8-9).
To his disciples, marriage without divorce essentially made marriage unworkable (“If this is the case, then it is neither profitable nor advisable to marry”). Jesus’ response was, “then don’t get married.” Actually he said that not everybody could accept the teaching, but some will renounce marriage “for the sake of the kingdom of heaven.”
So, even though Jesus uses the limited gender-binary language of Genesis, his answer here can also be applied to the question of same-sex marriage: Don’t let legal institutions separate what God has joined. More generally, don’t let the state supplant your morality with its laws by dictating what kind of society you will produce and reproduce. I cannot see how gender similarities or differences play into that teaching.
Elsewhere Jesus took an even more explicit stance on marriage:
The Sadducees, who say there is no resurrection, came to him with a question. “Teacher,” they said, “Moses told us that if a man dies without having children, his brother must marry the widow and raise up offspring for him. Now there were seven brothers among us. The first one married and died, and since he had no children, he left his wife to his brother. The same thing happened to the second and third brother, right on down to the seventh. Finally, the woman died. Now then, at the resurrection, whose wife will she be of the seven, since all of them were married to her?”
Jesus replied, “You are in error because you do not know the Scriptures or the power of God. At the resurrection people will neither marry nor be given in marriage; they will be like the angels in heaven. But about the resurrection of the dead—have you not read what God said to you, ‘I am the God of Abraham, the God of Isaac, and the God of Jacob’? He is not the God of the dead but of the living.” (Matthew 22:23-31)
Whatever literal resurrection the Sadducees had in mind which gave rise to paradoxes like the widow being married to all of her husbands in heaven, their vision was not the same as the one Jesus had been teaching in which “people will neither marry nor be given in marriage.” I don’t know what the hell he meant by “they will be like the angels in heaven,” but it’s clear that whatever the concerns of the Life that Jesus taught, marriage is not one of them. As such, I do not believe it is consistent for anyone to appeal to Jesus’ teachings to decide who should or should not be included in the legal institution of marriage, unless the answer is nobody. An appeal to Jesus in order to justify extending or denying the state privilege of marriage to certain populations requires ignoring the few things he is recorded as saying on the subject.
 Kinsley, Michael. “Abolish Marriage.” Slate. The Slate Group, July 2, 2003. Web. Accessed May 25, 2012. <http://www.slate.com/articles/news_and_politics/readme/2003/07/abolish_marriage.html>
 Many traditions, such as Catholicism, do place procreation as a primary purpose of marriage. The Second Vatican Council, for example, reemphasized that “the institution of matrimony itself and conjugal love are ordained for the procreation and education of children, and find in them their ultimate crown.” (Paul VI. Pastoral Constitution, Gaudium et Spes. 1965.)
 Okay, a fictional mathematician: Ian Malcolm from Michael Crichton’s Jurassic Park. In the motion picture adaptation, Dr. Malcom warns about the folly of trying to control the park’s population by cloning only female dinosaurs: “Life breaks free, expands to new territories, and crashes through barriers, painfully, maybe even dangerously … I’m simply saying that life finds a way.”