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. 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.

‘Pre-political Foundations’ focuses on the question of whether religion has a place in supplementing, if not originating, the civic spirit of constitutional regimes. Habermas’s starting point is the assumption that ‘the liberal state can satisfy its need for legitimation by drawing on the cognitive resources of a set of arguments that are independent of religious or metaphysical traditions’. But this is immediately qualified: markets—‘which, unlike state administrations, cannot be democratized’—are increasingly assuming ‘regulatory functions, in domains of life that used to be held together by norms’. Meanwhile, ‘civic privatism’ is being reinforced by a ‘discouraging loss of function in democratic opinion-formation’, as decision-making processes are displaced ‘onto supranational levels that are now beyond its reach’. Markets and bureaucracies are thus ‘displacing social solidarity from ever more domains of social life’. Yet the response is not to combat these trends, but rather to turn to religion in compensation, since ‘it is in the interest of the constitutional state to conserve all cultural sources that nurture citizens’ solidarity and their normative awareness.’ This then is an argument for the preservation of religion to save the endangered life of the constitutional state. To this end, non-believers must grant religious communities ‘public recognition for their functional contribution to the reproduction of desirable motives and attitudes’. In Habermas’s escalation of his civic-democratic encomium on faiths, modernity must be normatively experienced by non-believers as ‘a complementary learning process’, in which ‘religiously tone-deaf citizens’ are obliged ‘to determine the relation between faith and knowledge self-critically’, while also practising ‘a self-reflexive critical stance toward the limits of Enlightenment’.

Habermas here abandons his long-standing insistence on constitutional patriotism, in which sociality is regulated ‘reasonably and autonomously by means of positive law’—that is, etsi Deus non daretur: as if God did not exist. Instead, the political and cultural practice of the Enlightenment must atone for having unjustly contested the rights of the devout. In this view, the clause etsi Deus non daretur would be a heavy burden for the believer, since it compels him to renounce the God-argument, while for the secular citizen it is no burden at all. There is a clear contradiction with Habermas’s notion of the deliberative character of liberal democracy, which requires public argumentation to produce reasons ‘equally accessible to all’, and thus that every peremptory principle of authority be banished. It is inadmissible to reply to the question, ‘Why?’ with the absolutism of ‘Just because’. This does not just apply to believers: the public use of reason is supposed to exclude the use of ‘just because’ from any source—apart from ‘the market’, or ‘supranational levels’ beyond citizens’ reach.