For nearly 80 years, social critics of the Right and far Left have been trying to understand American liberalism by studying a specific social class. These critics share a belief that liberal ideas of a certain type dominate American life, and that they emerge from a social caste produced by American meritocracy. It's a class that sets the moral tone and imperatives for our society, that shapes our tastes and conversation.

One of the first attempts to dissect this tribe came from former Marxist turned conservative James Burnham, who theorized about an emerging "managerial class" that existed between capital and labor, and was made up of professionals, corporate executives, and executive administration officials. Like a good historical materialist, Burnham believed that material ambitions generated ideology. Using this as his guiding light, he hoped to understand and reveal the character of America's new elite, as well as determine what would happen to a country ruled by them.

In the 1960s and ’70s, neoconservative thinkers like Daniel Bell wrote about the "New Class," which was slightly less expansive in scope and focused mostly on professors and social scientists. A little later, the populist and left-leaning social historian Christopher Lasch wrote The Revolt of the Elites and the Betrayal of Democracy, slashing at the educated classes for abandoning socialist economics in favor of the politics of cultural revolution.

These theorists were offering a critique of the educated and liberal classes, with neoconservatives and socialists both lamenting the betrayal of older liberal ideas about the economy or about America's role in the world.

All three of these diverse theories have had a deep influence on modern conservative thinking in America. Many of my peers were influenced by Bell and Lasch, and I primarily by Burnham. But with the publication of Joseph Bottum's new collection, An Anxious Age: The Post-Protestant Ethic and the Spirit of America, I wonder if these earlier thinkers haven't all been surpassed.

Bottum's thesis is that there really isn't a new American caste. This "class" that has outsize influence on America's moral and spiritual life is roughly the same class that has always had it: Mainline Protestants, only now without the doctrinal Protestantism or the churchgoing.

Of course, on one level, the startling truth about the past 50 years of American social life is the collapse of Mainline Protestantism. In 1965, more than 50 percent of Americans belonged to the country's historic Protestant congregations. Now less than 10 percent do, and that number continues to drop. But Mainline Protestantism long existed as a column of American society, able to support the American project and criticize it prophetically at the same time. It would be even more startling if the spiritual energies it captained, and the anxieties it defined, ceased to exist the moment people walked out the door.

In Bottum's revisionist account, Protestant preacher Walter Rauschenbusch (1861–1918) looms as the figure who most succinctly defined the spiritual mission of 20th-century Mainline Protestantism and its heirs. He put "social sins" at the front of the Mainline imagination. "The six social sins, Rauschenbusch announced, were bigotry, the arrogance of power, the corruption of justice for personal ends, the madness of the mob, militarism, and class contempt," Bottum writes. These six would fittingly describe an enemies list for liberals today: racists and homophobes, hedge-funders who claim to be victims, the Koch brothers, the Tea Party, Dick Cheney and the neocons, and the Koch brothers again.

Not all of Bottum's post-Protestants are directly descended from Mainline members. Jews, Catholics, and even atheists join this unofficial spiritual-but-not-religious tribe, just as before many Jews, Catholics, and nonbelievers joined Mainline churches as a way to signal their arrival in a new, important social class. For Bottum it isn't quite right to define these post-Protestants as an elite — many of them are not at all wealthy, and do not have direct social power. Instead, they are an "elect" class, so named because they seem to constitute a churchly class: moralistic, possessed of self-superiority, and drawn from across economic classes, a mingling of poor artists, middlebrow activists, and rich benefactors.

For Bottum, what is remarkable is the way the spiritual experience of Rauschenbusch's "social gospel" is so like the experience of modern liberalism. According to Rauschenbusch, one opposes these social sins through direct action, legislative amelioration, and simply recognizing their effect and sympathizing with their victims. Rauschenbusch wrote, "An experience of religion through the medium of solidaristic social feeling is an experience of unusually high ethical quality, akin to that of the prophets of the Bible."

The post-Protestants Bottum identifies have just that, "a social gospel, without the gospel. For all of them, the sole proof of redemption is the holding of a proper sense of social ills. The only available confidence about their salvation, as something superadded to experience, is the self-esteem that comes with feeling they oppose the social evils of bigotry and power and the groupthink of the mob."

With the proper feeling comes a proper sense of guilt, and a missionary's zeal to correct wrongs. Over a century ago Rauschenbusch wrote, "If a man has drawn any religious feeling from Christ, his participation in the systematized oppression of civilization will, at least at times, seem an intolerable burden and guilt." Bottum deftly notes that in theological terms this signals "a nearly complete transfer of Christian fear and Christian assurance into a sensibility of the need for reform, a mysticism of the social order — the anxiety about salvation resolved by ecstatic transport into the feeling of social solidarity."

Can we not hear in the progressive's soul-searching examination of his own "privilege," as well as his unconscious participation in structural injustice, an echo of Rauschenbusch's words? Whereas Catholics make an examination of conscience before confession, and confess their personal sins before promising to amend their life, today's progressives examine their place in the social structure of oppression, and then vow to reform society. That is what it means to have a "social gospel without the gospel" — to be motivated by religious impulses, but believe it is entirely secular.

Bottum's theory also makes sense as theological-political genealogy. Rauschenbusch's main theological opponent was John Gresham Machen, a champion of Reformed Protestant theology, who founded Westminster Theological Seminary, one of the most important institutions informing conservative Evangelical life and thought. It makes sense that nearly 90 years later, conservative Evangelicals along with Catholics are still providing the lion's share of the moral and philosophical opposition to the heirs of this Mainline tradition. Then, as now, our political arguments are fed by a reservoir of religious and spiritual anxiety.

Besides providing an interpretive guide with great explanatory power for understanding modern American liberalism, Bottum's theory offers suggestions for further exploration. In an offhand way, Bottum notes that the more utopian and radically democratic impulses behind Occupy Wall Street would be recognized by any religiously literate age as those that lay behind the Radical Reformation. One can speculate that many of Occupy's members were once more-conventional liberals. Perhaps if the reformist impulses of our post-Mainline liberals continue to be frustrated, their spiritual longing for redemption will impel them toward radicalism as well.