Even before one defines religion he has to mark out at least something definitive or peculiar about it. Until recently, God was this definitive thing. For St. Thomas, for example, religion as simply justice activity towards God, but one could imagine loosening the definition to include discourse about God, or to include the care or devotion to things related to God. For various reasons (a desire to include Buddhism as a religion is usually given) we no longer take it as scientific or rigorous to take God as definitive of religion. This leaves us saying that something like transcendence or spirituality is definitive, and, as a consequence, those who are relating to God are really seeking him only so far as they are enthralled by transcendence. God is a contingent feature of such a quest.
William Cavanaugh has made a career over pointing out the problem in trying to make transcendence do the work that God used to do: what counts as a religion becomes arbitrary, and religion becomes defined as “personal and or subjective” (even when persons form a collective) whereas other sorts of transcendence (George Bush’s invoking of a providential plan for the extension of democracy to justify war in Iraq, or Anthony Kennedy invoking the transcendent mystery of liberty to justify abortion) are not seen as “religious” but as solid principles for public action, even ones worth killing and dying for.
A parallel problem arises in trying to speak about what is definitive or peculiar to sexual intercourse. You can define it as phallico-vaginal coupling,* but for even more reasons than we have to extend the meaning of religion, we also want to extend what counts as intercourse. The Contemporary Left has its own unique reasons for this, but there are also legal reasons too, like getting adequate accounts of rape, sexual assault, molestation, etc.. This has led to our Contemporary belief that “sex” is a genus that gets its specific difference from the orifice that modifies it. This is not merely a verbal reformulation, but carries with it the tacit belief that all these acts are the same sort of thing.** The problem is that this definition hides a radical chaos, a belief that sexual activity is really no objective thing at all. People seem to be working from an idea that a sexual activity is anything productive of orgasm, but ten seconds thought is enough to show that this definition will fail by all the same arguments that Contemporary persons level against the idea that sex is reproductive: all sorts of sexually active people don’t experience orgasms, and to define it in this way would give us monstrous and unsupportable accounts of molestation, rape, etc. All the same things could be said as sex being the expression of a sexual orientation (though this last definition would probably be even worse than the others, since it is not only unnecessary and too narrow but also viciously circular).
And so in both sex and religion we’re left having to give point to definitive properties that no majority of persons can be made to believe, and we want some definitive feature to be both arbitrary and not. We have no more of a definitive account of sex or religion than we have of ectoplasm, which would only be a problem for academics if not for the fact that we have inveterate and widespread desires for both of them, and with a need to codify what counts as sex (and a sexual relationship) in the eyes of the law.
*There are decent reasons for doing this: nothing in other sorts of sex corresponds to the sort of natural blooming of the phalico-vaginal: the phallus hardens, the vagina softens; the act forms a single natural entity, i.e. “that which reproduces itself” (but, as Schlasticism would put it, this happens in first act, not second, that is, sex is reproductive in the same way it is the sort of thing that leads to orgasm. Nature/ selection would no more favor every coupling to be fertile in second act than it would want every acorn to make an oak).
**STA, for example, would never use this sort of taxonomy of sexual activity. If one did propose such an account of sex to him, he’d see all adjectives other than phalic-vaginal coupling as alienating adjectives, like “artificial leather” or “white chocolate”.