I have been reading Margaret Farley’s Just Love: A Framework for Christian Ethics, the book that got the Vatican in a tizzy over renegade nuns several years ago under the grand inquisitor pope. To be fair, Just Love is more a feminist critique of Christian sexual ethics than it is a Christian sexual ethics, but the critique is apt and worth listening to. While Farley doesn’t fortify herself with Biblical chapter verse citations, her perspective makes sense to me when I consider sexuality under the lens of “I desire mercy not sacrifice.”
One of the things Farley rightly confronts her reader with is the way that Christian sexual ethics has inherited the heavy shadow that Platonism cast over early church fathers like Augustine. When sex is a problem because it involves a desire that is not strictly under the control of reason and for that reason it “disorders” the soul, then we are operating under a Platonic sexual ethic. Augustine, for example, cited the male erection as evidence of the “punishment” of original sin since it is a bodily function over which men do not have direct rational control.
I would argue that the “spirit” and “flesh” dichotomy that Paul works with is completely different than but easily conflated with the Platonic categories of reason vs. the passions and appetites. Spirit does not refer to disembodied pure reason; it refers to a body that is fully vital with the breath (pneuma) of God. Flesh does not refer to all things physical; it is the body reduced to a piece of meat. Bodily desire does not inherently make us “fleshly” and not “spiritual.” Rather, its tastes can be refined or degraded according to the habits and addictions we develop. When I talk to teenagers who smoke weed, I tell them that I can get high by fasting without tearing up my lungs. The reason I fast is not because I hate my body; it’s because I want my body to breathe God rather than being a sack of meat.
For much of Christian history, following Augustine and other church fathers, sex itself was considered an inherently love-disordering curse and product of the fall of Adam and Eve whose harm could only be minimized by making it strictly for procreative purposes, a view that the Roman church continued to hold well into the 20th century. The recent “celebrate sex within marriage” movement of neo-patriarchal American evangelicalism is a complete innovation and departure from centuries of Christian teaching that itself would never have happened except as a corrective refinement of the sexual revolution of the Sixties.
To me, sex is like wine. When you drink to get drunk, you become a disgusting sack of flesh; when you drink as part of creating a beautiful ambiance to enjoy with the one you love, it is a life-enhancing, sacramental form of worship. For this reason, I agree with Farley when she says:
The framework for sexual ethics that I have presented clearly does not treat sex as evil in some intrinsic way–not evil because of an uncontrollable biological urge, not evil because pleasure-seeking is inherently self-centered, not evil because the human body is a burden to the human soul. My proposed framework… does not yield conclusions such as: sex without openness to biological reproduction is evil because it involves unjustified “venereal pleasure.” It cannot yield conclusions such as: All sex as sex requires divine forgiveness, since it is inevitably tainted by a precious cataclysmic human “Fall.” 
This distinction makes a difference when talking about Christian sexual ethics because someone with a duty-based ethic is going to look through the Bible for rules to be obeyed for the sake of obedience while someone with a virtue-based ethic is going to look in the Bible for means to gain the virtues of the heart of Christ. For a virtue-based ethic, the point is to make it easier to act right. For a duty-based ethic, it’s supposed to be hard to act right since it’s about your reason contradicting your natural urges, so any ethical framework that sounds like it isn’t onerous or “sacrificial” enough is suspect for that reason. Virtue-based ethics is holiness for the sake of becoming a vessel of God’s mercy; duty-based ethics is holiness for the sake of performing a sacrifice to appease God. I really appreciated how Farley talks about virtue in this passage:
For Christians, the ideal is to integrate our loves somehow in an utter love of God. Our desire is for an integration that destroys no desire but transforms it, that ignores no love but makes it just, that harms no one, not even ourselves… Virtue in its classical meaning, after all, has to do with the refinement of our capacities so that we exercise them with consistency, greater ease, and delight. This virtue is not the pinch-faced virtue of either the fearful or the self-righteous; not is it the semblance of “purity” that is the enemy of generosity, humility, and full-hearted care. It is not the kind of freedom that is finally attained only by experimentation, keeping all options open, all forms of genuine relationship at bay. This freedom is, rather, the freedom of courage in the face of real risk and fear; perseverance in the face of weakness and distraction; trust in the face of self-doubt; faithfulness in the face of the furies or demons that would divert us both from the searches to which we are called and from our chosen and already anchored loves… This, then, is the freedom that unleashes just love, desire, and sex. [243-244]
Someone will say that Farley is being “anthropocentric” here. Virtue is supposed to be hard work and obedience; it’s not supposed to be the ability to exercise our capacities with ease and delight. What I hear in the need for virtue to be hard work and for God’s teachings about sexuality or anything else to serve the purpose of demanding obedience for obedience’s sake is a need for currency, the need for a transactional “sacrifice” by which I earn salvation. And what I hear in the exercise of capacities with ease and delight is a move from begrudging performance to joyful worship.