Given that this was an evangelical group they had a firm grasp on non-affirming positions regarding same-sex marriage. What they wanted my help with was discerning the shape of an affirming position regarding same-sex marriage, a position rooted in the Bible and Christian theology. This collection of intersecting arguments was something the group was less familiar with. So I was asked to help them map out and consider these arguments.
I wasn't allotted a lot of time to share, there were many others presenting along with me on different issues (e.g., the legal implications of Obergefell), so to prepare for my remarks I looked out over the landscape of this debate to locate, condense and summarize the main arguments that have been made by Christians for an affirming position regarding same-sex marriage.
Overall, I said, the affirming Christian position regarding same-sex marriage is built around one or some combination of four main arguments.
1. Apples and Oranges
Similar to the Copernican Revolution, when we came to recognize that the earth revolves around the sun, humanity has only just come to recognize sexual orientation as a durable and intrinsic feature of human sexuality. That is, sexual orientation is not a choice and it's not amenable to change.
Consequently, when the biblical authors, in both the Old and New Testaments, observed sexual activity they could only explain what they were seeing through the only lens they had, that of disordered and excessive sexual desire. That was the only reasonable explanation, in the eyes of the biblical writers, for why men would desire sex with men. Or women with women. What was being condemned in the Bible was this excessive and disordered sexual desire, desires deemed, given the science of the time, as being "contrary to nature."
We're in a very different situation today with our modern understanding of sexual orientation. When a teenage boy or girl, often raised in good, stable Christian homes, begins to experience same-sex desire during puberty we don't see those desires as intrinsically disordered or "contrary to nature." Even many conservative Christians have stopped condemning these desires as "unnatural."
All that to say, what the Bible condemns when in comes to human sexuality is licentiousness, sexual lust run amok. For the ancients, homosexuality appeared to be one among many examples of licentiousness, sexual desires so excessive and out of control that men could get to the point of desiring sex with other men.
An affirming position regarding same-sex marriage comes alongside the Bible in condemning licentiousness, same-sex and straight manifestations of it. But the affirming position recognizes that a same-sex couple who pledges life-long and monogamous fidelity to each other in the Christian sacrament of marriage don't fit what the Bible is condemning. It's apples and oranges. If anything, given that we recognize sexual orientation as natural (as even many conservative Christians now do), and that the marriage covenant is devoted to disciplining our sexuality--training eros to become agape--married same-sex Christians are the exact opposite of what the Bible is condemning.
Again, apples and oranges. What the Bible is condemning isn't what we're talking about in affirming same-sex Christian marriage.
As an example of this argument see Matthew Vines' God and the Gay Christian.
2. Marriage as Grace
"Male and female God created them" and "Be fruitful and multiply." Non-affirming views of same-sex marriage root their views of marriage in biological complementarity and biological reproduction. Marriage is between a man and a woman. In this Adam and Eve become the model of marriage, what we mean when we say that a marriage reflects the Image of God.
Affirming views of same-sex marriage argue, however, that there is another marriage found in the Bible, the marriage between God and Israel. This marriage is not based upon biology but upon election and grace. In this marriage the Image of God is witnessed in covenantal fidelity.
The primacy of grace over biology is also highlighted by Paul when he discusses the inclusion of the Gentiles into the church, the non-biological children who are grafted into Israel "contrary to nature" via the grace and election of God. This grace is also displayed in the family of the church, a family not formed through biology but through the Spirit and our pledges of covenantal fidelity to God and each other.
In short, an affirming position of same-sex marriage argues that marriages can reflect the Image of God in different ways. There are marriages and families in the Bible that are born out of grace and covenantal fidelity rather than biology.
As an example of this argument see Eugene Rogers' Sexuality and the Christian Body or Rowan Williams' essay "The Body's Grace."
3. The Holy Spirit Changing a Literal and Traditional Reading of the Bible
A huge hermeneutical crisis faced the early church when the Holy Spirit fell upon Cornelius and his household in Acts 10 and Peter allowed them to be baptized, formally bringing the Gentiles into the church and recognizing them as co-heirs of the covenant God made to Abraham. This was a hermeneutical crisis so big it split the church.
The issue was that circumcision was proclaimed by God to be an "everlasting" sign "in the flesh" of the covenant between God and Israel (Gen. 17.13). A plain and literal reading of the text argued that the Gentiles, therefore, would have to be circumcised to gain access to the promises made by God to Abraham.
And yet, the Holy Spirit was being poured out upon the uncircumcised. God was doing a new thing. Not just with Cornelius, but also with the Gentile converts in Antioch. How was the church to reconcile a plain, literal and centuries old traditional reading of the Bible in light of what was happening among the Gentile converts?
The issue came to a head in Acts 15 in what we call the First Apostolic Counsel. There the issues were debated--literal and traditional readings of Scripture clashing with experiences and testimony about the Holy Spirit at work among the uncircumcised. Hesitantly, the church decided in favor of experience and testimony over literal and traditional readings of Scripture.
In short, the Bible itself shows us how the action and activity of the Holy Spirit can guide the church toward different readings of Scripture, even overturning literal and traditional readings. Affirming views of same-sex marriage argue that something similar is happening in our time. We observe the fruits of the Spirit in same-sex unions, evidences of holiness, fidelity and grace. The same way the early Jewish Christians saw the fruits of the Spirit manifest among a group they knew to be--because the Bible told them so--sexually depraved and under the judgment and wrath of God.
For an example of this argument see Luke Timothy Johnson's Scripture and Discernment.
4. Love and Liberation
The fourth argument for an affirming position regarding same-sex marriage is a direct appeal to the Golden Rule: Love your neighbor as you love yourself.
In some hands this appeal is a simple appeal to love and compassion in embracing our shared humanity as beloved children of God in affirming same-sex marriages. 1 John 4.8: "Whoever does not love does not know God, because God is love."
In other hands, the appeal is for justice, often informed by a biblical and prophetic appeal to liberation theology: God's preferential option for those who are oppressed and suffering. Following the Hebrew prophets and Jesus' Nazareth Manifesto (Luke 4.16-21), the Bible must be read as "good news" for those who are suffering in the world due to hate, violence, oppression and marginalization. As it says in Romans 13.10: "Love does no harm to a neighbor."
For an example of this argument, on the love side more than liberation, see Gene Robinson's God Believes in Love.
Affirming Christian arguments for same-sex marriages, I told the evangelical organization, generally use one or some mixture of these four arguments. The arguments are nuanced, supplemented and blended in various ways, but these are the four recurring arguments.
For example, you can make the appeal for compassion and justice (Argument #4) more compelling and urgent by citing statistics about gay teen suicide and homelessness. The argument that the activity of the Holy Spirit affects how we read Scripture (Argument #3) can be supported in a variety of ways. A common example is how the Holy Spirit convicted the church about slavery. Evidences for how sexual orientation is now understood to be a natural and durable feature of our sexuality (Argument #1) and stories of the Spirit's fruits exhibited among gay Christians and same-sex couples (Arguments #2 and #3) are often given in memoir form (see Justin Lee's Torn).
Mixed, supplemented, nuanced and presented in various ways, these are the four main arguments for affirming same-sex marriages.