I'm still thinking about sex, but it's not just because I'm a man, and I'm pretty much always thinking about sex. It's because a few posts ago I sketched out some problems with inclusivist views of sexuality over against the ancient, traditional and Biblical depiction of sexual union as fundamentally heterosexual. My main point there was the fact that sexual union is theologically constructed on the foundation of God's covenantal union with His people. This, I said, prevents Christians from affirming homosexual union, because the mysterious projection of this covenantal relationship requires the difference of manhood and womanhood to retain the picture of monotheistic worship - i.e. the exclusive worship of the "Other". This, not a stock condemnation of Gentile behavior, is what undergirds Paul's condemnation of homosexuality in Romans 1:18-27. From the very beginning (in which the man and woman were created after God's own image) their complementarity afforded them the ability to image forth God's nature together in the advancement of His kingdom. Procreation was the means by which this was to be done, in the hopes of producing the "seed" by which the serpent's head would be crushed - but the essence of their sexuality was in their image-bearing capacity, not in their procreative agenda.
It's this image-bearing/representation that not only Paul is building from in Ephesians 5:28-33, but Moses builds upon in Deuteronomy 27:20-23. He prefaces this list of "cursing" for sexual vices with a clear statement of Israel's election and vocation in verses 9-10 (see also 28:12). Statements like these remind the reader that all of the commands to Israel recapitulate the command made to Adam, to bear God's image in the extension of God's kingdom over all the earth. In other words, sexuality is much more deeply rooted in Biblical theology than its occasional appearance in a vice/virtue list. It's bound together with the imago Dei and the unique manner in which heterosexual union pictures God and His relationship with His people. This bears itself out, of course, in Hosea, Jeremiah, Ezekiel and elsewhere.
Human sexual conduct is a function of Divine representation in covenantal union, which means that the theological significance of sexual union doesn't just prohibit homosexual behavior:
1) It prohibits bestiality: When God prohibits sex with animals in Lev. 18:23, he calls it "perversion". This word signifies a confusion of the created order. That perversion can be linked to the created order which distinguishes the creation of man and woman from the creation, which they are to rule over together. The distinction of the man and woman from the animals is prominently highlighted in Gen. 1:26-28 as based upon creation in his own likeness.
2) It prohibits incest: The Hebrew word "perversion" is also used of incest in Lev. 20:12 (with some versions even using that word to translate it), a crime which incurs the death penalty. Again, the reversal of the creation norm is the heart of the prohibition, and the resulting death re-narrates the consequences of the Fall.
3) It prohibits rape: Deut. 22:25-27 also echoes the Genesis account in comparing rape to (lit.) "a man who rises against his neighbor and murders him", carrying resonances of the Cain and Abel narrative with the same linkages between sin and death; but perhaps more importantly it likens the rationale for the death penalty to that of murder. Rape is a capital crime because it mars the image of God (see Gen. 6:9).
4) It prohibits polygamy: The theological significance of sexual union depends upon the exclusive relationship of one man and one woman. While this is less clear within the pages of the OT, whose patriarchs maintain multiple wives without express authorial censure (though the disastrous results of polygamy remain un-sanitized in these accounts - cf. Deut. 17:14-17, 21:15-17), the words of Jesus in the NT clearly place the Genesis narrative at the foundation of theological considerations about sex (see Mat. 19:4-8).
5) It prohibits adultery and prostitution: The imagery of adultery and prostitution provides the most powerful imagery in God's rebuke of Israel for her waywardness to the covenant relationship which wed them together with YHWH in the exodus event. Ezekiel 16 and Hosea 1-4 are the bizarro Ephesians 5. The stability of sexual union depends upon the imagery of devoted monotheistic worship, and the opposite is also true; the chaos of adultery and prostitution is patterned after idolatry. Notice that the coherence of God's complaint prioritizes passionate love and expectations of covenant loyalty in the institution of marriage - not just procreation. The "knowledge of God" and Adam "knowing his wife" are unavoidable parallels.
6) It prohibits pre-marital sex: The primacy of "covenant" in describing God's relationship with His people stands behind the "mystery" defined in Ephesians 5. The betrothal of the Bride to Christ is sealed by baptism, with public vows. Witnesses attest to the covenant, a role assigned to the creation in God's union with Israel. In the same way, the marriage vow re-enacts the cosmic drama of God's saving purposes and sanctifies the relationship as more than just the harlequin romances of passing desire.
The act of sex is a consummation of this thick description, not in the conscious thought of imaging God's love for His people and not in a procreative agenda, but in the uninhibited expression of the lovers' passion for one another. The tangled bodies of men and women in the act of sex is a monument to God's love, much like communion proclaims the Lord's death - not in words but in the eating of it. But in order for this mysterious representation to redound to the glory of God, it must not only be heterosexual - it must be exclusive, within the bounds of covenantal commitment, with the utmost respect of the image-bearing partner and as the consummation of a relationship characterized by self-giving love.