This book derives from a discussion in 2007 between Habermas and representatives of Munich's Jesuit School for Philosophy. The book's subject is why and how secular thinking should engage religion. The first chapter – ‘Habermas and Religion’, by Michael Reder and Josef Schmidt (who are credited as editors in the original German version of the book) – functions as an introduction. The second chapter, entitled ‘An Awareness of What is Missing’, is by Habermas. The next four chapters are responses to the Awareness essay by Norbert Brieskorn, Reder, Friedo Ricken, and Schmidt, respectively. In a seventh chapter, Habermas responds to his interlocutors. I shall call Habermas' chapter ‘the Awareness essay’, and the seventh chapter ‘the Reply’.

The introductory chapter gives the following helpful background to the Awareness essay. Until the mid or late 1980s, Habermas held that, in a just society, rational discussion would supersede religion in promoting moral action and preserving social cohesion. However, Habermas did worry about the likelihood of such a result; and, within the same period, he suggested that the creation of a just society required some sort of secular appropriation or translation of religion. Habermas's more recent work, including a discussion with the Pope, develops the latter thought – as does the Awareness essay.

The Awareness essay begins (15–16) by recounting a funeral of the writer Max Frisch. Frisch was ‘an agnostic who rejected any profession of faith’. So the funeral ceremony was not religious. But it was held in a church. According to Habermas, Frisch

More: the ceremony ‘tells us something about secular reason, namely that it is unsettled by the opaqueness of its merely apparently clarified relation to religion.’ Habermas continues:

Habermas wants to clarify this relation between philosophy and religion, and to see how, in a ‘post-secular society’ – a liberal or pluralistic society wherein religion remains significant (7; cf. 37) – religion and ‘secular reason’ might help one another. To those ends, Habermas proposes a dialogue between religion and secular reason. But the dialogue is to be constrained on each side. Religion must recognise scientific truths and accept ‘the basic principles of universalistic egalitarianism in law and morality’. And secular reason ‘may not set itself up as the judge concerning truths of faith, even though in the end it can accept as reasonable only what it can turn into its own, in principle universally acceptable, discourses’ (all 16).

All of this could be clearer. It becomes clearer when one better appreciates the range of lacks – of things that, detrimentally, are ‘missing’ – with which Habermas is concerned. (The chapters by Brieskorn and Ricken are of some help in revealing those lacks. But the analysis that follows is largely my own.) Three of the lacks at issue are lacks on the part of, and only on the part of, secular reason or secular life. First here is an epistemic lack. It consists in a lack of awareness of, of sensitivity or aliveness to, various morally relevant states of affairs and especially bad states of affairs. Second, there is a motivational lack consisting in a lack of motivation for acting morally. Third, there is a ceremonial lack: an absence of those rites which would endow some secular practices such as burial with greater significance or aptness. A fourth lack is on the part of religious people. This justificatory lack, as we may call it, consists in the fact that (sometimes) the contributions that religious persons make to moral and political discourse are too religious to engage secular persons. Finally, there is a legitimation lack. This consists in a shortfall of support by religious citizens for their liberal democratic state and, to that extent, a general or unqualified lack of political legitimacy.

Surely each of the lacks does exist to at least some degree. And the lacks are interconnected. The knowledge at issue in the epistemic lack is a necessary condition for the motivation at issue in the motivational lack. Actually, if one holds that to perceive a normative state of affairs is to be motivated in the corresponding way, then the epistemic and motivational lacks are identical. Adorno – a major inspiration for the trope of something's being missing (11 n. 5) – likely accepts that identity. I am unsure that Habermas does. Next: if one mitigates the epistemic lack by secularising religious ideas (rather than in some other way, if there is another way) then that is to mitigate the justificatory lack. For, a secular but religiously-inspired articulation of normative states of affairs amounts to a secular justification for religious concerns. Finally: a mitigation of the justificatory lack might encourage the religious to support the liberal state, thereby mitigating the legitimation lack.

The reasons for the restrictions upon the envisaged dialogue are now discernible. If the religious party rejects science and/or universalistic egalitarianism, then religious contributions to normative matters will not engage secular persons and the justificatory and legitimation lacks will persist. As to the restrictions upon the secular party, note that the Awareness piece presents secular reason as ‘postmetaphysical’, which means, at least, that such thinking rejects metaphysics qua supernaturalism. But often religion does seem to involve metaphysics in that sense. Hence a refusal to hear any metaphysics from religion would likely end the dialogue and afortiori forestall any progress the dialogue could have made with any of the lacks. Hence the condition that ‘secular reason’ ‘may not set itself up as the judge concerning truths of faith’. However, while the secular party will listen to metaphysics, it will not, ultimately, accept it: ‘in the end’, secular reason ‘can accept as reasonable only what it can turn into its own [. .] discourses.’ So Habermas does indeed intend a (or various kinds of) translation or appropriation or religion.

That intention creates tension between Habermas and some of his contributors. Reder insists that, contrary to what he sees as Habermas' tendency to ‘instrumentalize’ (39) religion, religion is much more than ‘a motivational resource’ (ibid). For one thing – Reder proposes – religion is something that transcends full rational comprehension. That claim seems to be intended as irreducibly metaphysical. One can compare Schmidt's chapter. Schmidt declares that, ‘Religion has absolutely no reason to fear the dialogue with enlightened reason’ (69). But he insists that debate about a ‘metaphysical’ (70) God must continue. The problem here – the problem disclosed by Reder and Schmidt – is both practical and theoretical. The practical problem is that the religious may find the refusal to take metaphysics seriously – to take it seriously as metaphysics – to be as off-putting as a simple ban upon that kind of talk. The theoretical problem is that it is unclear what either party could gain from the dialogue. As one might put it: what use, or even content, is there for a religion deprived of religion? But of course Habermas' whole hypothesis or hope is that there can be a dialogue that will yield ideas that mitigate the lacks. How far does the book substantiate that hope?

I begin upon that question by considering a proposal by Ricken. To wit: a kind of translation, from the secular to the religious, will ‘enable us to see [certain] phenomena, force us to confront them, and trigger our responses’ (53). The idea is the following somewhat Hegelian one. Philosophical ideas have religious precursors that are more arresting and more motivating than they themselves are. Hence if we draw attention to the precursors, a basically secular reason will increase its affective punch. Ricken little illustrates or specifies his procedure. But Habermas, who proposes the same idea under the heading of a ‘genealogy of reason’ (19), gives plausible examples of philosophical concepts ‘infused with experiences and connotations which stem from the biblical teaching and its connotations’ (80). The examples include emancipation, community and solidarity. But Habermas makes little of the affective nature of such concepts. What he does do, is to elaborate the more epistemic side of Ricken's proposal. For the Reply considers how religious ideas or formulations can recall aspects of phenomena that, often because of scientism (18 and 22) we have forgotten.

Scientism – from which Habermas disassociates his postmetaphysical thinking – is this view: natural science is the only source of knowledge. (Or at least that is one of the formulations of scientism to be found in Habermas' corpus. Note also that, according to Habermas 2003, scientism can encourage the use of some genetic technologies which should not be permitted.) Habermas: ‘biblical motifs can remind us, for example, of dimensions of a reasonable personal self-understanding which have been abandoned too hastily’ (82). Habermas uses two ideas from his interlocutors to illustrate. Ricken supplies the first (although actually he himself is enlisting Habermas 2003). It is a matter, according to the Reply, ‘of clarifying the limits of human self-objectification and self-manipulation’ (82). The idea is this. That God created man in His image is construable thus: no human should try to impose an identity upon another. So far as it goes, this idea does speak to most of the lacks. The second idea is Schmidt's. Schmidt tries to secularise the notion that, in his words, ‘worship of the one God liberates human beings from all possible idols and earthly powers’ (63). Habermas' secular construal of the conception is an idea about how language both constrains and liberates us. But no weighty sense of something's ‘being missing’ seems at issue here. Note further that the ceremonial lack very largely drops out of the book after Habermas's initial illustration of it.

I conclude that the book makes a start in identifying, or parsing, religious ideas that could help with the lacks. But – even, I think, when combined with other work by Habermas – it makes only a start. More work is needed. Moreover, if that work is to remedy the lacks, then, clearly enough, the ideas in question need to become widely influential. So, what are the prospects for this enterprise of identification and dissemination?

Consider first the secular appropriation, or imitation, of religious rites. At one point, Habermas dismisses the ‘Californian syncretism of pseudoscientific and esoteric doctrines’ (78). An anxiety about such syncretism is that it is a bricolage of elements which have no real connection with each other. But won't the same arbitrariness beset the appropriation of rites for which Habermas seems to hope? Perhaps not. Witness ‘Death of God’ theology and deism, each of which, to a degree, might be said to rid religion of metaphysics. Also, some forms or interpretations of Buddhism (and the Reply mentions Buddhism briefly) posit no God and even, perhaps, nothing (else) supernatural. Yet such Buddhism has its rites and – indeed, and partly thereby – motivates its members. Some forms of humanism may be comparable. So the idea of secular rites has a plausibility.

But there is problem. The idea of secular rites is an old one. So too is that of translation from religious to secular language. (Habermas is well of aware of that last fact and cites Derrida as one recent practitioner of the enterprise.) How effective can Habermas' proposed solutions be, if the lacks they mean to remedy persist despite previous application of those solutions? One might retort that the solutions – or their dissemination – have not been pursued enough. Still, Habermas himself seems pessimistic about the outlook. ‘I suspect’, he writes (74)

A little more remains to be said. First: engagement with existing analyses of religious language would have improved the book (although as Reder notes Habermas does engage elsewhere with Wittgenstein's ideas about religious language). Next: much of the book, including the Awareness essay, is harder to understand than it should be. Part of the difficulty is that there are many gratuitously ambiguous formulations. However, approximately half of the ambiguities are absent from the German original. Moreover, much that is unclear in this book is clarified by Habermas' Between Naturalism and Religion (a text wherein, inter alia, Habermas relates his concerns with religion to Rawls' notion of public reason, engages with Kant' philosophy of religion, and argues against reductively naturalistic views of human nature). Last and least: there are typographical mistakes on pages 12 (‘reforms’ instead of ‘forms’), 18 (‘cannot cope on its own’ instead of ‘can cope on its own’!), and 35 (‘recoguition’ instead of ‘recognition’); and the binding of my copy was poor (20 pages fell out).

Verdict: this book, which is best read in conjunction with other work by Habermas, identifies serious problems; but the merits of its solutions are uncertain.