Over at the Public Discourse, University of Texas sociologist Mark Regnerus offers a preview of forthcoming data revealing how support for or opposition to same-sex marriage shapes a person’s larger worldview and beliefs about sexuality.

He asks: “What is the sexual and relational morality of Christians who accept the moral legitimacy of same-sex marriages?”

His data from the forthcoming Relationships in America Survey reveals an interesting, if not totally unexpected result: that church-attending Christians who support same-sex marriage look more worldly and less Christian. Churchgoing Christians who support same-sex marriage also register support for other beliefs about sexuality that Christianity has historically considered taboo.

According to Regnerus, churchgoing Christians (who were comparably much fewer in number as a pool of respondents), register much higher support for pornography, cohabitation, casual sex, and higher support than the general population for abortion rights.

Regnerus’ sampling method is worthy of praise. In contrast to blithe surveys that merely report the opinions of all those who identify with a particular religious affiliation regardless of observance, Regnerus does the important work of determining what those in the pews actually believe. A political poll that didn’t differentiate between likely and unlikely voters wouldn’t be an accurate representation of the electorate, and for the same reasons, a survey should distinguish between someone who merely answers “Catholic” or “Baptist” when asked for a religious identity and someone who actually shows up on Sunday.

Building off that, two conclusions can be reached. First, it’s hard to find churchgoing Christians who support same-sex marriage, but that would be expected given the implosion happening in liberal denominations. Second, those who support same-sex marriage are more likely to hold what would traditionally be considered “worldly” beliefs out of step with the Christian tradition. That’s important. If Christianity teaches one system of belief about sexuality and liberalism teaches another, it would be difficult to consider oneself authentically Christian while holding to beliefs that Christianity has unequivocally condemned.

What does this data reveal from a larger moral perspective about the shifts taking place in sexual morality across America? They reveal how comprehensive an indicator sexuality is of a person’s worldview. As Regnerus states, “In reality, our moral systems concerning sex and sexuality tend rather to resemble personalized ‘tool kits’ reflecting distinctive visions of the purpose of sex and significant relationships (and their proper timing), the meaning of things like marriage and gender roles, and basic ideas about rights, goods, and privacy.”

As Russell Moore and I wrote at National Review Online in July, Regnerus’s study reaffirms that “sexuality isn’t ancillary to Christianity, in the way some other cultural or political issues are. Marriage and sex point, the Bible says, to a picture of the gospel itself, the union of Christ and his church. This is why the Bible spends so much time, as some critics would put it, ‘obsessed’ with sex. That’s why, historically, churches that liberalize on sex tend to liberalize themselves right out of Christianity itself.”

Regnerus says as much himself: “Churchgoing Christians who support same-sex marriage look very much like the country as a whole — the population average (visible in the [above table’s] third column). That answers my original question. What would a pro-SSM Christian sexual morality look like? The national average — the norm — that’s what.”

It may seem too simple to infer, but the conclusion begs to be written: Liberal sexual beliefs work, in the long run, to make fewer Christians.

The great Presbyterian divine J. Gresham Machen, once wrote that “modern liberalism not only is a different religion from Christianity but belongs in a totally different class of religions.”

When it comes to the sexual revolution, one unmistakably catalyzed by liberalism’s own design, Machen continues to be right.

—Andrew Walker is Director of Policy Studies for the Ethics and Religious Liberty Commission.