The Anglican Communion Institute's "The Holy Scriptures and the Teaching of the Church Universal on Human Sexuality"
Despite its long-winded title, this piece is refreshingly brief; I will try to follow suit (it is near the bottom of the ACI's "Articles" section). It purports to set out "[t]he continuous teaching of the Church," namely "a consistent word" about "God's intention for human sexuality" implicit in both testaments. While the strategy of starting with biblical theology is laudable, I doubt the paper succeeds.
First, let's make some relatively superficial criticisms of the paper. According to it,
marriage is instituted inGenesis "as a means" to God's "creative purpose for humanity." In Genesis the eternal purpose is being fruitful and multiplying. In Ephesians et al., the marriage covenant "reflects" God's eternal purpose--a purpose prima facie having nothing to do with reproduction, but rather our salvation. For a paper boasting a consistent word, some work remains: What is marriage for? Reproducing, or reflecting salvation? First, how are these to be fitted together? Second, how is homosexual union inconsistent with reflecting salvation?
Remember: for Paul, being single is permissible, and at least as honorable as being married. Yet, "within the Church...male and female are to be in a covenant relationship of marriage that reflects God's eternal purpose." Note the imperative "force" of "to be": males and females in the Church Ought to be married; from this it follows that nobody in the Church is Permitted to be single. The paper's claim is too strong, contradicting Paul. That is, there is no general rule obligating heterosexual marriage for any individual male or female in the Church. Nor does such a general rule follow from the creation of male and female in Genesis.
Is it true that "African, Asian, and other non-Western cultures have the language, the lifestyle, and the support systems for homosexuality familiar to the West"? Prima facie, that is just incredible. It seems the West has an array of legal protections and socio-economic opportunities absent throughout many of the nations of the rest of the Anglican Communion for gays. E.g. how many Nigerian gay couples can have legally recognized unions in Nigeria, as is possible in Spain, and even the U.S.?
II. Small changes could preserve the paper's general argument from my complaints in section I. So, on to a more serious point: "homosexual practice" from Leviticus to Romans and elsewhere is "a clear rebellion against God's created purpose" be that reproducing or reflecting salvation, according to the paper.
The point isn't that homosexual "practice" precludes or is inconsistent with reproduction, for instance--that would be false anyhow. Gay men and lesbians could meet solely for the purpose of reproduction, and then divide the children between them, for instance. Rather, God has issued a certain command about how reproduction should be carried out: by married heterosexual couples. It is the fact of God's command that counts. Presumably something similar could be said for reflecting salvation: God gets to decide what counts as a permissible reflection by fiat; only heterosexual marriage does, and asking "Why?" is out of place. Our proper place is to obey the command.
Is there any answer to such an argument from divine command? Set aside reasons to question divine command theory per se, or whether divine command theory is genuinely Biblical. I want to keep common ground with ACI; the proper way to give an answer is to start with the Bible, from premises the authors of the paper would accept. Here I rely on the argument in my second post. The paper admits the "Church is the Bride of Christ" and that marriage is a "covenant relationship" that "reflects God's eternal purpose." Ephesians is even stronger--marriage is to be modeled after the relationship of Christ to the Church. Given such premises, it follows gay marriage is permissible: the relation of Christ to the Church includes the relation of male to male (a male Christ to a male Church member, each resurrected). If marriage here below is to be modeled after a relation in which males are relata, men can be the relata in marriage here below.
I don't think ACI anticipated an argument like mine when they were writing this piece. Thus it is no surprise that I can say they err in taking prohibitions of homosexual practice to preclude homosexual marriage. Perhaps the prohibitions against homosexual practice are part of a general prohibition against unchaste action and fornication: in general sex outside of marriage is sinful between anyone. If that were the case, a marriage covenant between gay partners would make sex between them permissible. That counterfactual holds even for conservatives at ACI. Thus, their case requires more argument--bringing up marriage as reflecting salvation opens up the possibility of referring to the eschatological state after which marriage here below is to be modeled. They have to somehow keep the normative grip of the eschatological state while denying it permits gay marriage. Good luck!