Theological ideas,” Mark Lilla tells us, “still inflame the ideas of men, stirring up messianic passions that leave societies in ruins.” But Western intellectuals disdainful of religious conviction are ill-equipped to understand a world where Muslim physicians drive gasoline-filled trucks into the Glasgow airport. They don’t even understand their own history, in which the problem of “political theology” was once central. Lilla thinks we can no longer afford such complacency. The “fragility of our world” demands a reexamination of how societies tame the “destructive forces of biblical religion.”

It’s an intriguing premise and a powerful, if often puzzling, book. Over the past decade, Lilla’s crisp, learned sketches of European intellectuals, often first appearing in the New York Review of Books and the New Republic, have deservedly captured a wide readership. (Many are collected in Lilla’s The Reckless Mind: Intellectuals in Politics.)

Lilla also recently published an essay in the New York Times Magazine detailing his adolescent religious journey, from a Catholic parish in suburban Detroit to Evangelicalism to the Catholic charismatic movement and beyond. Having read nothing but Mad magazine, histories of the World Wars, and the Hardy Boys until age fourteen, Lilla was handed a Bible walking out of a Christian rock concert he had attended on a lark. “Like most Catholics back then, and perhaps even now, I had never held a Bible in my hand.” He immersed himself in the text and reemerged as a teenaged scriptural literalist, prowling the halls of his high school wearing a large leather cross around his neck. “I relished,” he wryly recalls, “being a prophet without honor in my own homeroom.”

The Stillborn God might have benefited from this self-deprecating touch. Lilla is never less than lucid, and the erudition on display is impressive, but the first two-thirds of the book are determinedly abstract, moving from Great Thinker to Great Thinker, Hobbes to Locke to Rousseau to Kant. For Lilla, the problem of “political theology” is the habitual human desire to look to God to organize not just religious but political life. It’s an understandable impulse-why shouldn’t a transcendent God offer political guidance?-but potentially a disastrous one, as Protestants and Catholics slaughtering each other during the Reformation discovered.

Philosophers such as Thomas Hobbes and John Locke then postulated a world where religious ideas did not directly inspire political forms, where politics could proceed independent of church affiliation. Locke, in particular, made the “powerful claim, which we now take to be self-evident, that churches are voluntary associations dedicated to the private worship of believers and should be treated as such.” (John Courtney Murray might gasp at this sentence, as would many other Christians, Jews, and Muslims enthusiastic about the U.S. Constitution but unwilling to relegate religious beliefs to private worship.) Among Locke’s intellectual descendants, the American Founders wrote a determinedly secular Constitution even as they hoped that their silence on religion would allow its flourishing. “What began as a thought experiment,” Lilla concludes, “thus became an experiment in living what we inherited.”

The story in nineteenth-century Europe was less happy. In Germany, especially, philosophers and theologians welded nationalism to a particular liberal version of Protestantism. (Here Lilla exaggerates the distance between the Anglo-American and the continental experience, since Protestantism-and anti-Catholicism-in nineteenth-century Britain, Canada, and the United States also marked civic identity.) This German Protestantism, associated with Hegel, Friedrich Schleiermacher, and Ernst Troeltsch was shorn of most creedal elements, but celebrated religion as an underpinning for modern ideals of individual freedom and economic progress. Religion became less about God than about the social bonds forged among believers. Many Jewish thinkers, too, also modernized liturgical doctrines and practices and saw themselves as allied with the great Protestant theologians, and, poignantly in light of mid-twentieth-century totalitarianism, the Germany of Kant, Goethe, and Beethoven. The simultaneous explosion of biblical scholarship in Germany during the nineteenth century further focused attention on the supposedly more authentic Jesus of the Gospels, shorn of ecclesiastical accretions.

The slaughter of World War I destroyed ideals of the inevitability of progress and with it the moral foundations of this liberal Protestantism and liberal Judaism. The enthusiastic support initially given to the German war effort by leading Protestant theologians such as Adolf Von Harnack and Troeltsch, matched by support from leading Jews such as Hermann Cohen, who pleaded with American Jews not to fight the Kaiser, led to widespread disillusionment. This is Lilla’s “stillborn God.”

Then a twist. Having marched his readers through the great figures in Western political philosophy, Lilla comes to his conclusion. The reader turns the pages with anticipation. How will Lilla define the problem of political theology now?

The answer: two theologians from 1920s Germany, Karl Barth and Franz Rosenzweig.

Barth is well known, and Lilla rehearses the familiar story of Barth’s thundering challenge to liberal Protestantism, especially his insistence, in his 1919 commentary on Paul’s Letter to the Romans, that Christians repent before an unknowable, inscrutable God. Barth once urged believers to read the daily newspaper as a kind of duty, and he favored socialism as an economic program, but he thought politics itself a sideshow to the eschatological drama faced by each human being.

Rosenzweig is less well known. But interest in Rosenzweig is increasing, as suggested by two fine recent books, one by Peter Gordon and the other by Samuel Moyn, which stress Rosenzweig’s importance not only for German-Jewish history but German history broadly considered. Rosenzweig, like Barth, took an antihistorical view of religion and urged Jews to focus their immediate attention on God’s promise of redemption. (Lilla does not discuss any Catholic figures. He defends this decision by alluding to the church’s hostile attitude toward modern society in the early twentieth century and consequent separation from the intellectual currents he details here. Perhaps, but Karl Barth influenced not only Franz Rosenzweig but also Hans Urs von Balthasar, Hans Küng, and many other Catholic theologians, as Fergus Kerr has recently reminded us in his excellent Twentieth Century Catholic Theologians.)

Because both Barth and Rosenzweig practiced a negative political theology, demanding that believers get right with God before worrying about always transient political structures, Lilla sees them as the crucial figures opening the door to a more dangerous view of politics, a “theological messianism” once thought buried by the Reformation. Even more provocatively, Barth and Rosenzweig, and the apocalyptic rhetoric they favored, “shaped a new and noxious form of political argument, which was the theological celebration of modern tyranny.” Lilla even goes so far as to link Barth and Rosenzweig-“unwittingly”-to the same Weimar talk of crisis that launched the career of a young Bavarian rabble-rouser, Adolf Hitler.

These are strong claims, and the problem, as Lilla immediately recognizes, is that while some of Barth’s followers supported Hitler, others did not, and Barth himself famously denounced German church leaders for prostrating themselves before the Nazis. Moreover, many of Barth’s liberal theological foes supported Hitler. It seems a stretch, then, to conclude, as Lilla does, that Barth’s followers who became Nazis betrayed Barth’s principles but remained consistent with his rhetoric.

Even if Barth and Rosenzweig’s denunciation of liberal theology inadvertently opened the door for more radical figures, ending The Stillborn God in this fashion remains a peculiar choice. I can’t help but wonder if an exasperated editor at Knopf pleaded with Lilla to make more gestures toward contemporary relevance. In a recent New York Times Magazine essay, Lilla discussed the pressing question of how Westerners must engage Islam, sensibly concluding that Americans and Europeans should pay special attention to the efforts of Tariq Ramadan and Abou El Fadl to uncover resources within Islam to aid in navigating modernity. He also smartly dissects Iranian President Mahmoud Ahmadinejad’s open letter to President George W. Bush, with its taunt that “liberalism and Western Democracy” seem doomed before the “will of God.”

But none of this appears in The Stillborn God. And Lilla utters nary a word on the American Evangelicalism of his youth beyond an oblique warning that only “a strong constitutional structure and various lucky breaks” have prevented political theology from dominating “the American political mind.” Instead, his conclusion is more austere. Those Westerners devoted to the modern separation of religion and the state must realize that they remain the exception, that only their “own lucidity” can sustain this important experiment.

Fair enough, but perhaps overly som¬ber. “Theological messianism” remains a possibility in most societies at most times, as is messianism of any sort. But the ideal of religious freedom seems much more stable now than in the 1920s, and certainly more stable than at the moment of the American founding. Political leaders in Turkey, China, and Nigeria now honor the ideal, whatever their actual practice, in much the same manner that East Germans called their nation a Democratic Republic. That some Middle Eastern governments, notably Saudi Arabia, do not make even a pretense of protecting religious freedom is viewed as scandalous. In this sense Western notions of religious freedom are no longer idiosyncratic. Instead, they provide the underpinning for what increasingly seems a global human right, important in Melbourne but also in Mumbai, necessary for Chicago but also for Cairo.