Statistics from the most recent Gallup poll indicate that Americans’ moral views have become increasingly liberal over the past 14 years, with U.S. citizens tending to approve of behavior they would have deemed immoral or sinful just a generation ago.

The biggest change percentage-wise has been in Americans’ positive moral evaluation of polygamy and human cloning, both of which more than doubled since first measured by Gallup in the early 2000s. In 2003, a mere 7% thought that polygamy was morally acceptable, whereas in 2015, the figure has grown to 16%. Similarly, the recent poll found that 15% of Americans now accept human cloning, up from just 7% of the population in 2001.

Approval of gay and lesbian relations has also soared in the same time period, with an absolute majority of 63% of the population now seeing nothing wrong with this behavior, as opposed to 40% in 2001—an increase of 23 percent.

In 2001, a majority of 53% of U.S. citizens already approved of fornication, and this group has continued to swell also, with 68% now viewing sex between unmarried people as morally unproblematic. The study found, in fact, that in nearly all of the 16 categories compared, Americans’ moral views had shifted left, with the exception of only two: the death penalty and scientific experimentation on animals.

Unsurprisingly, the leftward shift in Americans’ moral views has been matched by a corresponding loss of religiosity. A recent Pew Center study on religion in the United States found that despite America’s reputation as one of the more religious countries in the world, it has experienced a notable dip in religiosity in the past seven years.

The religious category to take the biggest hit was Christianity, especially “mainline” Christianity, which fell by 3.4 percent. Though the United States is still a statistically “Christian nation,” with about 70% identifying themselves as followers of Jesus, it is markedly less so than even a generation ago.

Evangelicalism, on the other hand, saw significantly smaller losses than mainline Protestant churches, dropping less than one percent of its adherents during this same period. Those identifying as Evangelicals fell from 26.3 to 25.4% for a total loss in membership of just 0.9%.

Though it is impossible to establish a strict causal relationship between the two phenomena of moral liberalism and declining religiosity, the correlation between them is still striking.

What may not seem immediately apparent is why as Americans become increasingly progressive, they are abandoning liberal religious denominations in favor of conservative ones.

One theory, advanced by Arthur E. Farnsley II, a professor of religious studies at Indiana University, is that the more churches resemble society at large in terms of their moral teachings and understanding of the meaning of human existence, the less relevant they are. Why continue to attend church services to hear the same message you get from reigning culture? Religion only makes a difference when it offers an alternative account of reality, distinguishable from secular culture.

It is, in fact, the countercultural religious groups that are holding on to their membership.

Farnsley suggests, therefore, that the more liberal religious groups will continue to lose members and influence “because they are already on the modernist side, meaning many of their core values are expressed in other institutions, including government.”

Much of the decline in membership for mainstream Christianity seems to be the result of a loss of recognizable Christian identity in those churches. Four particular phenomena stand out in this trend away from Christian tradition.

In the first place, mainstream Christian churches have shifted focus from the worship of God to social justice issues. As churches have moved away from a God-centered vision to a human-centered approach, they have come to resemble many other philanthropic institutions with no particularly religious character. As churches look more and more like humanitarian associations, the allegiance of their members has dropped correspondingly.

A second discernible phenomenon has been the unmooring of mainstream Christianity from its biblical roots. Many Christians seem to find Christ’s moral teachings increasingly embarrassing in an age that is tolerant of virtually any consensual human behavior. Abandoning a more literal approach to biblical morality, many have reinterpreted even the clearest biblical doctrines to make them resemble societal trends. As sociological criteria have replaced biblical principles as a moral guide, the Bible has been reduced to a source of “spiritual inspiration.” Having lost their belief in the power of the Bible to teach moral truth, many have drifted away from Christianity altogether.

A third development has been a shift in emphasis from eternity to the here and now. Traditionally, Christianity placed greater importance on the “salvation of souls” than on the immediate benefits of religion, meaning that more attention was given to the “eternal truths” of final judgment, heaven and hell, than to the psychological rewards of faith. As mainstream Christians have abandoned talk of eternity in favor of secular concerns, they have found that “secular” solutions seem better suited to meet their needs.

A final trend among mainstream Christian churches has been a progressive lowering of the moral bar, seemingly out of fear of appearing “judgmental” or “hypocritical.” Confusing judgmentalism with the ability to tell right from wrong, many Christians have moved in the direction of withdrawing disapproval from all but the most egregious sins. The lower the bar, the fewer fail to get over it: “I’m okay. You’re okay.” Similarly, some have confused hypocrisy with a simple failure to live up to one’s moral ideals, and have embraced the facile solution of chucking their ideals. Hypocrisy, in fact, becomes impossible when one no longer endorses any moral standards.

What all this means for the future is uncertain, but there are no signs of a reversal of the liberalizing trend any time soon. It seems, rather, to be gaining momentum.

The message for churches, however, seems relatively clear. For those who wish to hold on to their members and possibly even attract new ones, a recovery of a clearer Christian identity is indispensable, even at the risk of appearing countercultural.

Follow Thomas D. Williams on Twitter @tdwilliamsrome.