The sheer intensity of this turn in Habermas’s concerns is striking, especially in a thinker who has never betrayed any sign of personal faith. Habermas was and apparently remains “religiously unmusical” (to cite Weber’s famous phrase). But at least one critic has announced this as a “turn” in Habermas’s thinking, prompting the thought that we may be witnessing an intellectual conversio, after the Latin vertere, to turn or to change. When he delivered his acceptance speech at the Paulskirche, Habermas was well past his seventy-first birthday: one could imagine he had entered upon a phase of thinking where the former confidence in systematic reason is giving way before the existential questions that confront us all. One could even characterize this phase as a Spätstil, or late style—a term that his teacher Adorno used to describe the more fragmentary and experimental compositions of the aging Beethoven.

But such talk of a secular conversion in Habermas’s recent work risks serious misunderstanding. Readers sympathetic to religion may rush to conclude that the paradigmatic philosopher of modern reason has at last seen the light, while stolid advocates of secularism may despair that a cherished ally has fled the camp. The worst (and clumsiest) mistake appeared in a 2010 New York Times column by Stanley Fish, who announced that Habermas had come to recognize the “inability” of secular society “to go it alone.” The problem is not merely that “going it alone” is too casual a phrase to capture Habermas’s intentions. Fish sought to prove this idea by quoting a line by Habermas that appears in the editor’s introduction to An Awareness of What Is Missing. “Among the modern societies,” Habermas wrote, “only those that are able to introduce into the secular domain the essential contents of their religious traditions which point beyond the merely human realm will also be able to rescue the substance of the human.” It is a striking turn of phrase, but its significance is uncertain. Did Habermas mean to say that religion contains insights indispensable for humanity, insights that secular reason cannot surpass? Fish thought so. The problem is that the German editor was quoting from a speech Habermas gave for the eightieth birthday of Gershom Scholem, the great historian of Jewish mysticism, more than thirty years ago, and Habermas was explaining Scholem’s perspective, not his own.

To understand what Habermas is really up to in his most recent work requires the kind of patience and precision that has been in terrifically short supply in much of the popular controversies concerning the place of religion in modern politics. It is our good fortune that much of what Habermas has written now appears in English collections—Religion and Rationality: Essays on Reason, God, and Modernity (2002) and The Frankfurt School on Religion (2004)—both edited by Eduardo Mendieta, who brings to this task a rare combination of theological sensitivity and theoretical rigor. When viewed in this wider perspective, Habermas’s turn to religion no longer comes as a great surprise. On the contrary, it should strike us as a natural amplification of philosophical and political themes that have preoccupied him for many years.

HABERMAS CAME TO maturity as a philosopher in the left-Hegelian tradition of Western Marxism, which typically excoriated religion as an illusory diversion from the profane task of this-worldly redemption. In his Contribution to the Critique of Hegel’s Philosophy of Right in 1843, Marx offered a definition: “Religion is the sigh of the oppressed creature, the heart of a heartless world, and the soul of soulless conditions.” He then added the famous line: “It is the opium of the people.” But Marx did not mean to suggest that getting over religion was a simple affair of casting aside false beliefs. (The opium-analogy is revealing: kicking a drug habit is hardly easy.) The thought was that religion serves a compensatory function insofar as it offers an unfree humanity a fantasy—an image of happiness—that reconciles them to their present unhappiness. This is why one cannot hope to redeem humanity from its unhappiness if one confines oneself only to the intellectual criticism of religion. One has to change the unhappy conditions for which religion offers compensation: “The abolition of religion as the illusory happiness of the people is the demand for their real happiness. To call on them to give up their illusions about their condition is to call on them to give up a condition that requires illusions. The criticism of religion is, therefore, in embryo, the criticism of that vale of tears of which religion is the halo.” But there is an ambiguity in this theory. Did Marx mean to suggest that religion does nothing but conspire to obscure the actual conditions of our unhappiness? That is an observation only about the social function of religion rather than its propositional content. Marx also seemed to be saying that religion may contain the right insights—our suffering must be overcome, our hope for happiness deserves satisfaction—only those insights are applied to the wrong realm, a metaphysical beyond rather than the profane space of human action.