Since 1848, discussion of the democratic republic in Europe has been grounded in secular reason. Politically, its legitimation has been based on appeals to popular sovereignty; normatively, it rests on the rule of law. The will of God plays no part. If any one figure has embodied this discourse over the past half-century it has been Jürgen Habermas, who has long argued that the constitutional state must embody universalizable principles, whereas religious precepts are accepted only by that particular religion’s believers.footnote1 Indeed, writing in the 1990s he argued that, given the slow but steady secularization of society, religious reason would survive in the West only ‘as long as no better words for what religion can say are found in the medium of rational discourse’. It was the task of secular philosophy to translate the moral and intellectual riches of religious thinking into earthly terms, as Kant had carried over the distinction between ‘is’ and ‘ought’ from Christian ethics.

The past ten years, however, have brought a significant shift—some have called it a veritable Kehre—in Habermas’s thinking on the permissible role of religion in political life. In October 2001, just weeks after the attacks on the World Trade Center, he gave an address in the Paulskirche in Frankfurt under the title ‘Faith and Knowledge’. Although he would later find reasons to support the us attack on Afghanistan, his initial reaction was to deplore any notion of a ‘war against terrorism’. Instead, confronted with the ‘fatally speechless clash of worlds’, the task was ‘to work out a common language beyond the mute violence of terrorists or missiles’. Islamist fundamentalism had to be understood in the context of the painful, uncompensated uprooting that modernization had wrought upon traditional forms of life. The attentats demanded the West reflect on its still-incomplete secularization, if it was not to appear either as ‘crusaders for a competing religion’ or ‘salespeople of instrumental reason and a destructive secularism’. The organized religions must agree to the premise of ‘a constitutional state grounded in profane morality’, but in exchange secular societies should be open to the ‘resources of meaning’ that religions might contain: ‘the mode for non-destructive secularization is translation’—on this basis, ‘intercultural relations may find a language other than that of the market and the military alone’.

By January 2004, in an exchange with the then-Cardinal Ratzinger at the Katholische Akademie of Bavaria, notable for the consensus between philosopher and priest, Habermas bent much farther. His contribution, ‘Pre-political Foundations of the Constitutional State’, now argued that the political generalization of a secularized worldview was ‘incompatible’ with the neutrality of the state towards different outlooks. ‘Secular citizens may neither deny that religious worldviews are, in principle, capable of truth, nor question the right of their devout fellow-citizens to couch their contributions to public discussions in religious language.’ Three months later, in Łodz, he delivered a further lecture on ‘Religion in the Public Sphere’. In this instance the focus was not so much the Islamic world or Bavarian Catholicism as the United States, the great example of a constitutional state whose founding aim was ‘promoting peaceful religious pluralism’; the role of religion in political life was examined through John Rawls’s conception of the ‘public use of reason’.

These two essays constitute the thematic core of Habermas’s collection, Between Naturalism and Religion, recently published in English. In his Introduction, Habermas characterizes the present age as marked both by the spread of naturalistic worldviews—endorsing spectacular advances in biogenetics, brain research and robotics, even where these are driven by ‘eugenic motives’—and by the unexpected revitalization and politicization of religious traditions across the world. From the point of view of normative democratic theory, these conflicting trends also demonstrate ‘a tacit complicity’—both conspiring to jeopardize the cohesion of the polity, since neither side appears willing to engage in self-reflection. This is the linking thread of Between Naturalism and Religion, which aims to confront the ‘opposed, yet complementary, challenges of naturalism and religion’ with a ‘stubborn metaphysical insistence on the normative meaning of a detranscendentalized reason’. In fact, the book is both more and less than this. It collects eleven essays, only six of which can truly be assimilated to the unitary theme of ‘naturalism and religion’. In addition, it includes an engagingly conversational autobiographical reflection, ‘Biographical Roots of Two Motifs in My Thought’, while the other five essays revolve around two venerable philosophical debates: whether or not an ethical cognitivism is possible, i.e., whether norms can be rationally deduced on the basis of de facto ascertainments; and the still more classical question of the possibility of free will in a deterministic physical universe, to which our brains belong. These are issues that Habermas has analysed more systematically and at greater length elsewhere. The genuine novelty however, which makes this book stand out from other miscellaneous collections of the vast, and inevitably repetitious, Habermasian production, are the texts dedicated to the role of religion in democratic society. In particular, ‘Pre-political Foundations of the Constitutional State’ and ‘Religion in the Public Sphere’ crystallize a new development in Habermas’s political thinking, and therefore deserve analytical attention.

What Habermas is proposing here is a squaring of the circle: upholding liberal-democratic principles, according to his normatively demanding republican schema, while at the same time recognizing religious ‘reasons’—that is, argumentation and political motivations that have recourse to God—as not only legitimate, but as useful and, ultimately, essential elements of liberal-democratic sociality. This recognition entails the duty of non-religious citizens to translate into secular terms the ‘intuitions’ that religious citizens can only fully express in terms of their faith. Without this co-operative attitude, believers would unfairly shoulder the burden of tolerance towards competing worldviews, and thus would be discriminated against. Non-believers are required to open their minds to the potential truth of religious worldviews.