Readers looking for orientation to Habermas's post-2001 engagement (Auseinandersetzung) with religion will find his 2005 essay on Kant a useful place to enter the conversation that has reached its climax with the publication of these two volumes on faith and knowledge. Habermas began his two-decade long investigation of world religions, and Christianity in particular, from the perspective of “how one can assimilate the semantic legacy of religious traditions without effacing the boundary between faith and knowledge.”Footnote ¹ I do not find any significant break with the project he announced fifteen years ago. What he said then applies equally now: “I distinguish between rationalist approaches that (in the Hegelian tradition) subsume [aufheben] the substance of faith into the philosophical concept, from dialogical approaches that (following Karl Jaspers) adopt a critical attitude towards religious traditions while at the same time being open to learning from them.”Footnote ²

Habermas's notion of religion as a spur to civilizational dialogue, and moral and social learning useful to the human species as a whole, contains an implicit evolutionary philosophy of history. For the residents of a planet that seems to be spinning out of control, the message that humanity has a potential to evolve and learn may sound Panglossian. But Habermas philosophizes in a different, more sober and chastened, mood, one that was in evidence fifteen years ago: “Pure practical reason can no longer be so confident of its ability to counteract a mobilization spinning out of control armed solely with the insights of a theory of justice. The latter lacks the creativity of linguistic world-disclosure that a normative consciousness afflicted with accelerating decline requires in order to regenerate itself.”Footnote ³ Habermas's faith in reason is grounded in the ever fragile and reversible, but still remarkable, achievements of institutions that protect and include the freedom of the other as bearer of equal rights, including the right to difference (2:794).

I call attention to the role of Habermas as historian. What advantage did he imagine from writing a history of the discourse on faith and knowledge in Western thought? He says that he is aiming at a genealogy of postmetaphysical thinking, but why is genealogical history a useful supplement to his well-known achievements in philosophical argumentation?

I believe that Habermas has turned to history for reassurance regarding the fate of reason in global human society. In “Modernity's Consciousness of Time and Its Need for Self-Reassurance,” he wrote: “Modernity can and will no longer borrow the criteria by which it takes its orientation from the models supplied by another epoch: it has to create its normativity out of itself.”Footnote ⁴ This is still the condition of postmetaphysical reason, which Habermas has desubstantialized, proceduralized, and linguistified, as Martin Jay has pointed out.Footnote ⁵ But now Habermas has also attempted to historicize it. By focusing on the relationship between faith and knowledge in the tradition of Western philosophy, he provides a new strategy for achieving modernity's self-reassurance. If we want to understand “why we accept that certain cognitive practices can be trusted to produce rational and generally binding results, then we must become clear how [philosophical] techniques other than secular and postmetaphysical ones became implausible.” Habermas says that “historical cross-checking” (Gegenprüfung) is a more promising mode of self-reassurance than probing the boundaries of postmetaphysical knowledge in an “unmediated” way (1:68, also 2:767). Through a reconstruction of its “historical learning-steps” (historische Lernschritten), Western philosophers can scrutinize the attainment of a postmetaphysical perspective on the specificity of Western experience, and the contingency of Western history. By avowing its provincial Western origins, philosophy arrives more modestly clothed to the postcolonial conversation of humanity.

In “The Occidental developmental path and the universality claim of postmetaphysical reason,” Habermas elaborates on the justification for the genealogical approach to Western thought: “Because the same dialectical tension between tradition and modernity, from which the Occidental shape of modernity once arose, now operates in other civilizational complexes” (1:117). To render the claim of postmetaphysical thought to “general validity,” it is helpful, he asserts, to stage the intercultural discourse in such a way that “affinities” between “similar developmental paths” and “the parallelism of learning processes” (Lernprozesse) become visible (1:134). Habermas writes that all the “great civilizations” share a root in the “similarly structured worldviews of the Axial Age.” He does not justify his use of the category, with its implied hierarchy over lesser, unnamed civilizations, or nations that do not belong to greater “civilizational” units. But he clarifies that “all civilizations go through the same evolutionary stages,” facing the challenges of coming to terms with nature and of social integration (1:134–35). Indeed, one of the most impressive features of Habermas's volume is the extent to which he has engaged the voluminous literature on world religions, and the need to recognize the plurality of formations of the secular-cum-religious that are discussed under the rubric of “multiple modernities” (1:110–35).

“Learning processes” are one of the most important leitmotifs of these two volumes. And the prevalence of the concept puts one in mind of Habermas's writings from the 1970s in which he tried to “reconstruct” historical materialism with a focus on the development of normativity. In both cases there is a focus on a species-wide human subject. As he wrote in 1976, “Whereas Marx localized the learning processes that release epochal developments . . . in the forces of production, there are in the meantime good reasons for assuming that learning processes also take place in the dimension of moral insight, practical knowledge, communicative action and the consensual regulation of conflicts.”Footnote ⁶ The “normative structures” that result from these learning processes form the essential “pacemaker [Schrittmacher] of social evolution.”Footnote ⁷

The present volumes describe reason in a similar manner: “What we call ‘reason’ is only the subjective reflection of the sociocultural life-form of linguistically socialized subjects who not only cannot not learn [but also that] the historical shape of their life-forms continually change and . . . can be improved in rational ways. . . . The life-form of Homo Sapiens is twinned with advances [mit Fortschritten verschwistert]” (1:174). The second volume concludes on the same note. “We can measure moral progress in institutions which improve the potential for the solution of social conflicts between individuals and collectives in consensual and nonviolent ways” (2:791) Our moral horizons of concern—who we consider part of the “we”—often shifts in dramatic historical surges (Schübe) (2:792). And history is where we can look for the “traces” (Spuren) of this progress: “Moral-practical learning is as possible as cognitive learning and is undisputed in child development. To his question, “does practical reason leave traces of generation-spanning learning-processes in a people in the historical shape of ‘moral progress,’” his answer is a resolute yes (2:789, also 2:763, 2:778).

Law was always a preoccupation, a source of fascination, and key dimension of Habermas's oeuvre from the late 1950s onwards.Footnote ⁸ It is a mistake therefore to imagine that his dialogue with John Rawls from the beginning of the 1980s marked a turn from Critical Theory to a liberalism satisfied with the status quo. Since the beginning, Frankfurt School theorists understood that the Rechtsstaat could be a resource for socialism, and redeemed from its limitations by immanent critique.Footnote ⁹ His deep engagement with legal and constitutional theory in the 1980s and 1990s signified no capitulation to really-existing liberalism.Footnote ¹⁰ As he put it in the early 1980s German debates on civil disobedience, “The paradox of the Rechtsstaat is that it must embody positive law but also stand for principles which transcend it, and by which positive law may be judged.” Like modernity, the Rechtstaat was an unfinished project, indeed one that cannot be finished at all. “The history of the development of basic rights in Europe is best understood as the history of a learning process, [and] who will claim that this learning process is at an end?”Footnote ¹¹

Given the importance of constitutions as sites of social learning in Habermas's earlier work, it is not surprising that the democratic Rechtsstaat retains its privileged place in his philosophical system. “For a genealogy of postmetaphysical thinking,” he writes, “constitution-giving processes and the fate of democratic Rechtstaaten are of special significance.” This is because they permit one to scrutinize the institutional embodiments of reason—“and their corruption”—through a discourse-theoretical reading in the spirit of the Left-Hegelians (2:763). The constitutionally secured practices of citizens to private and public autonomy offer, in principle, and often in practice too, the opportunity to better the conditions of their common life. These practices are the concrete manifestation of “rational freedom” (vernünftige Freiheit), the fruit of Habermas's reconstruction of the history of Western philosophy, since they show that it has “acquired a certain historical efficacy, however uncertain” (2:802).

In Between Facts and Norms, the mature of statement of his political theory, Habermas argued for the co-originality of human rights and popular sovereignty as the animating principles of the democratic Rechtsstaat. It was always interesting that a man who had seen the radicality of the Unrechtsstaat in his youth in the 1930s did not allow the rights foundationalism of the German constitution to stand without protesting too much. On the contrary, he devoted a great deal of energy to critiquing the power of the judiciary in postwar Germany. When implemented from above and by fiat in the form of a paternalistic welfare state, human rights were instrumentalized and stripped of their solidaristic power. Given this background, it is tempting to read Habermas's genealogy of the rights-bearing subject, a major theme in the present volumes, as an effort to balance out his republican leanings with a fresh look at the tradition of natural rights.Footnote ¹²

This he provides in a stunning discussion of the emergence of “subjective” natural rights from the “objective” tradition of Catholic natural law in which it was once embedded. Protestantism marked the beginning of the “anthropocentric turn” and the “trailblazer [Bahnbrecher] of postmetaphysical thought” (2:14). In a discussion that stretches from Luther to Hobbes, Spinoza, and Locke, Habermas traces the origins of natural rights to the “juridification” of the state of nature (2:920). The discovery of the New World allowed them to see that Christian Europe was “only a province of the community of nations” (Völkergemeinschaft). Through a close reading of Francisco de Vitoria's and Francisco Suarez's accounts of the rights-bearing person, he finds in the concept of the dominium sui “the core meaning of the modern concept of legal autonomy” (1:87). With these volumes, Habermas also offers a new account of the origins of the Western discourse of rights. As such, it contributes admirably to the ongoing global conversation about the changing meanings of secularism, modernity, and liberalism.