Early on in volume 1 of AGPh, Habermas devotes a section to the question of generalizable validity: “The Western Path of Development and the Universal Claims of Postmetaphysical Thinking” (1:110–35). He acknowledges the unabashed Eurocentric focus of the book's main narrative as well as the ways in which past claims to universal validity have been used by the West as justifications for domination and exploitation. He also accepts that, on the surface anyway, the best a genealogy of Western philosophy can do is make a case for the “internal validity” of postmetaphysical reason and not its “external validity.” This leads to the conclusion that the universal validity of postmetaphysical claims (like all validity claims) needs to be defended in a global intercultural discourse in which all participants are on an equal footing and open to learning (1:111). But seeing as postmetaphysical reason is procedural and discursive with reason-giving as its lodestone, doesn't this “test” already presuppose the validity of postmetaphysical thinking? I interrogate the circularity of invoking intercultural dialogue to test the validity of the procedures of intercultural dialogue. Despite its problems, I argue that such a dialogue, understood pragmatically as a fallible, open-ended process of problem solving over time, is the only avenue to push past, and answer accusations of, Eurocentric domination.

Habermas introduces three themes in discussing the possibility of an intercultural discourse that could vindicate postmetaphysical reason. The first is to challenge any incommensurability thesis claiming that civilizations or traditions are hermetically sealed worlds, not open to mutual understanding, deep comparison, or mutual learning. The second is to outline the functional imperatives that point to the need for such a discourse in the ever-growing network of international law and economics. Finally, he takes up what such a discourse might look like through a thought experiment.

Habermas rejects the view that the West is the index case of modernization. Instead, he argues that modernization is a global trend within which different cultural traditions develop in different directions and along different paths. All cultures must deal with a globalized social infrastructure affected by the power of science and technology, the bureaucratization of societal coordination, and the imperatives of capitalist wealth accumulation (1:119, 127). The interesting question is the interpretive stand they take towards these forces, a stand that is informed by their distinctive cultural trajectories. These distinctive cultural trajectories are in turn tied to the religious traditions that emerged from the Axial Age. There is no claim that other cultures will follow the same path as the West; indeed it is clear that other cultures have been following different paths. But these divergent paths are bookended by a common cognitive revolution of the Axial Age and a globalized modernity that no culture can escape. Thus, Habermas's narrative involves the uniqueness of the Western trajectory within a larger context of shared potential and shared fate.

The Western trajectory is in many ways an exception that was shaped by the contingent yet constitutive split between faith and knowledge. Thus, the question is not, what are the various levels of modernization across the globe? (taking the West as the index case), but rather, what are the various self-understandings of modernity and one's place in relation to these global phenomena? This embrace of some version of the multiple modernities argument does not downplay the radical dissonance and sometimes outright hostility that exists between the various interpretations of modernity. But it does do some brush clearing in rejecting the “clash of civilizations” take on modernity. The Axial Age and the multiple-modernities argument taken together suggest that there is a potential for a fruitful study of comparative civilizations that challenges any incommensurability thesis and opens the possibility for intercultural dialogue.

The global reach of modernity across all world cultures is accelerated by developments within international law and transnational regulation. Classical realist models of international relations are less and less plausible as the global web of interdependence, legal regulation, international organizations, and cooperation grows denser. The proliferation and intensification of law, regulation, and organizations is driven by the need to solve coordination problems at the supra-state level. Climate, energy, trade, finance, crime, weapons, humanitarian disasters, refugees, and of course pandemics are just some of the issue areas the control of which escapes the uncoordinated isolated actions of nation states (1:124). As the network of legal and regulative coordination becomes denser and the need for such coordination in the face of crisis more intense, the lack of legitimate and effective steering institutions becomes destabilizing. Habermas suggests that these developments put the constitutionalization of international law and a politically constituted world society without a world government on the horizon for exploration (1:125). Such a projection moves the discussion from a descriptive claim about global regulation and interdependence to a normative claim about legitimacy. With this, he returns to the possibility of an intercultural discourse, now, however, directed at agreement on basic constitutional principles of international political justice.

Habermas proposes a thought experiment in which we imagine what this global intercultural dialogue would have to look like if it were to underpin the legitimacy of norms that are to govern the coexistence of a multicultural world society. This thought experiment does not start with the question, “what would the parties agree to?” but rather, “what are the cognitive presuppositions we would have to make to imagine any head-way towards agreement given the different starting points?” (1:125–26).

The thought experiment begins with interlocutors divided by the religious and metaphysical worldviews to emerge from the Axial Age. Two stages of reflexivity must be reached to successfully engage in a discourse that could legitimize global political norms and justify global principles of justice. Participants will first have accepted what Habermas calls weak secularism (1:130). Here agreements (for example on universal human rights) represent a point of convergence (a sort of overlapping consensus) between the cultural traditions and comprehensive worldviews. Each individual position might still be rooted in a particular religious worldview, but the agreement is based on the idea of common overlap and not religious principles. He calls this weakly secular because acceptability is tied to a point of convergence. Convergence is a secular standard that overrides exclusive possession of revealed truth and requires that participants become reflexively aware of the difference between their deeply held cultural and religious beliefs and the value and importance of finding common ground with dialogue partners to underpin and justify common norms of actions. Habermas thinks all major worldviews in the modern world have more or less embraced this level of reflexivity in ongoing debates about global norms.

The second, more demanding stage of learning would involve the acceptance of a stronger sense of secular reasons. Convergence can function to underpin coordination, but mere convergence cannot justify a norm in a strong sense. Thus, the second phase of the intercultural dialogue requires the acknowledgment that only freestanding substantively secular reasons, ones that are always open to discursive challenge and that could be accepted by anybody, can underpin shared principles of justice.

We have come full circle. The opening question was, what would an intercultural dialogue that could vindicate the universal claims of postmetaphysical thinking look like? The answer is that it would have to be governed by the procedural requirements of postmetaphysical reason. Habermas fully acknowledges that the thought experiment seems to give the secular West an unfair advantage in setting the very rules of the conversation (1:133). There is no getting around this problem. Appealing to the genealogy of these rules can at least show that the West came to them by way of a long-drawn-out learning process sparked precisely by the need to find common norms under conditions of radical disagreement. But it still suggests that the only test of the validity of postmetaphysical reason is derived from postmetaphysical reason.

This circularity might not be quite as damning as it appears. Habermas, it seems to me, is not saying other cultures need to adopt our standards in order to see the value of our standards. Nor is he saying that the price of admission into a global society is the adoption of Western standards. Philosophy does not come up with ideas and then try to sell them to the world. Philosophy reconstructs and clarifies self-understandings that are in turn produced by ongoing problem-solving, especially challenges facing integration and coordination. He is suggesting that the proof is in the pudding in the sense that we are being forced by global coordination crises to engage in intercultural dialogues, negotiations, and problem solving. These dialogues contain a learning potential in which we come to see the sorts of conditions that would make agreements stable and outcomes justified.

The West does not teach the rest; the pragmatics of coexistence opens this potential. It opens this for everyone including teaching the West (through the criticism of postcolonial thinking, for example) the ways it has inexcusably and atrociously undermined this potential. But perhaps this way of looking at it is even more damning because it supposes a sort of inexorable march of postmetaphysical reason driven by the functional necessities of coordination. But there is no inexorability or inevitability to the Habermasian story. Indeed, he is often very pessimistic about the likelihood that we will solve our global problems, let alone do so in a fair and just way.

The question we began with was whether the internal validity of postmetaphysical reason translated into an external validity. The arc of the larger historical narrative and the brief discussion of intercultural dialogue blur the distinction between internal and external. The fallibility of postmetaphysical procedural reason always pushes in the direction of inclusion: more voices, more reasons, more arguments, more criticisms, more participants, more perspectives. Thus, it always pushes against a line between internal and external. But the hope is that bringing what was outside, inside the circle of dialogue and discourse does not assimilate or drown out the new inclusion but expands dialogue and creates a space for that included voice to freely speak, challenge, and take up a yes/no stand to any and all proposals.

We should read the final stage of the dialogic thought experiments not as an entry requirement—only freestanding secular reasons that we could all agree upon may be appealed to—but as Habermas's projection of what would have to be the case to reach full and complete justification according to a postmetaphysical standard. But full and complete justification is always out of reach in this imperfect world of incomplete procedures, inadequate processes, and fallible participants. What becomes important in the meantime is the procedural conditions of equal and open participation in processes of collective problem-solving that can potentially launch a learning process whereby we learn what works and what does not. At the core of this view is the idea that coercion and brute force are inherently unstable for beings who are communicative and so are norm following. Norm following calls for justification; justification under conditions of pluralism requires embracing procedural ideals of equality and freedom.