Rudolf Langthaler, professor of Christian philosophy at the University of Vienna, has written and edited numerous books on the philosophy of religion in recent years. This is his second voluminous take on Kant, after his Habilitationsschrift Kants Ethik als ‘System der Zwecke’ (Berlin: de Gruyter 1991). Geschichte, Ethik und Religion im Anschluss an Kant consists of two volumes which encompass almost 1,300 pages. This is in all likelihood Langthaler’s opus magnum, not only in terms of length but also in terms of depth, scholarly erudition and scope.

The subtitle denotes Kant’s overall philosophical enterprise or ‘project’, the attempt to establish a new, critical metaphysics which avoids the pitfalls of both scepticism and dogmatism. Kant’s attempt was historically sensitive; in the first part of his book, Langthaler shows how Kant located his own philosophy within the ‘history of pure reason’, with the goal of a practical transition (Überschritt) to the supersensible while not being oblivious to the self-preservation (Selbsterhaltung) of reason (vol. i, pp. 37–248). The book falls into three parts: the first volume reconstructs Kant’s metaphysics ‘in ihrem dritten Stadium’ (Progress of Metaphysics, 20: 301) with an emphasis on the just mentioned ‘archaeology of reason’, the philosophy of history and the ‘highest ends’ (höchste Zwecke) of reason. The second, most important and I think most fascinating part is a systematic reconstruction of religion within Kant’s overall philosophy. The last part is an expedition at the ‘borders’ of practical reason, with Kant’s philosophy as the starting point but going beyond Kant’s texts, in particular with respect to an authentic theodicy.

The book develops Kantian ‘motives’ or central themes such as the self-preservation of reason, the teleologia rationis humanae, the world concept (Weltbegriff) of philosophy and the vocation of the human species. It is simply impossible to cover all aspects and parts of this book in one review. Therefore, I am going to focus on what can be considered the most controversial (and I think also the best) part of the book, Langthaler’s reconstruction of Kant’s central doctrine of the philosophy of religion (vol. ii, pp. 13–363): ‘Morality thus inevitably leads to religion, and through religion it extends itself to the idea of a mighty moral lawgiver outside the human being, in whose will the final end (of the creation of the world) is what can and at the same ought to be the final human end’ (Religion, 6: 6).Footnote ¹ Of course Langthaler knows about the central place of the doctrine of the highest good in this respect, and he gives it its due place in the system (vol. ii, pp. 93–147). Yet his approach is original. First, he tries to show how the self-preservation of reason can be considered the basis of rational faith (vol. ii, pp. 148–293; cf. Refl. 2446, 16: 371–2). Given the Archimedean point of practical freedom (vol. i, pp. 119–20, 506), it is for the sake of the self-preservation of reason that the ‘moralisch konsequente Denkungsart’ or way of thinking is led to the holding-to-be-true (Fürwahrhalten) of the final end of practical reason. Secondly, Langthaler claims that Kant’s arguments in favour of moral religion should be read as ‘existenzialanthropologisch’ (vol. i, pp. 26–32, and vol. ii, pp. 16–40, 94–5, 223): it is a first-person perspective, it includes the knowledge that humans are individuals who have bodies, needs and interests, also in the wholeness of their existence, and that they are beings with purposiveness.

Langthaler emphasizes three aspects in Kant’s transition from morality to religion. First, he demonstrates the insufficiency of the philosophy of history. He claims that like Benjamin or Horkheimer – who wrote in the wake of totalitarianism, of world wars and the Holocaust – Kant was fully aware of the irreversibility of past suffering and injustice, even if there should be juridical (and perhaps even moral) progress in history, with a happy ending in the long run (vol. ii, pp. 424–33). If we do not curtail the concept of the highest good, if we do not drop the crucial element of a necessary connection of morality and appropriate happiness ‘as ground and consequent’ (vol. i, pp. 428–9, 432; cf. KpV, 5: 111), then we have serious problems with any immanent philosophy of history – and with any, even an ‘authentic’, attempt at theodicy (as Langthaler readily admits, even insists upon; see vol. ii, pp. 537–637). Secondly, Langthaler emphasizes what is called Strafwürdigkeit in German and sometimes rendered as ‘punishability’: based on the dignity of the perpetrator, any violation of the moral law deserves to be punished. If this punishment did not take place, justice would be deficient and the unconditional moral law would not have significance and meaning. ‘Blood innocently shed cries out for vengeance. … belief in a future life does not, properly speaking, come first, so as to let the effect of criminal justice upon it be seen; on the contrary, it is from the necessity of punishment that the inference to a future life is drawn’ (Metaphysics of Morals, 6: 490 and note; see Langthaler’s discussion in vol. ii, pp. 97–104). Finally, there is the familiar reading of the highest good: there ought to be a moral world to avoid a final moral absurdity. The virtuous person might manage to bear and suffer a world without divine justice and hope in the salvation of the victims of history, but it could not be affirmed and accepted from a moral perspective. Morality would still have a meaning, but not full meaning. In the words of Langthaler: ‘Zwar unbedingt sinnhaft, weil moralisch geboten, obgleich nicht sinnvoll – sondern letztendlich buchstäblich belanglos, d.h. mit Blick “auf den moralischen Lauf der Welt” sowie auf “das Ganze seiner Existenz” im Letzten doch ohne umgreifende und auch endgültige “Bewandtnis”’ (vol. ii, p. 108).

This book has many merits. It is a brilliant defence of the metaphysical Kant interpretation. It offers a new ‘existenzialanthropologische’ perspective. It outlines changes in the Critical philosophy after 1781 (e.g. vol. ii, pp. 294ff.). It focuses on, interprets and makes use of Kant’s subtle, profound and important distinctions that are often glossed over. For instance, Langthaler draws our attention to the difference between object per se and object in the idea (vol. i, p. 80), between suppositio relativa and absoluta (vol. i, p. 81), ‘bloß vernünftigem Wesen’ and ‘Vernunftwesen’ (vol. i, p. 118), between juridical and ethical legality (vol. i, p. 231) and so on. Langthaler’s overall assessment of Kant’s enterprise is very positive; it is, he claims, not only relevant for contemporary philosophies but even ‘indispensable’ (vol. i, p. 13).

This book is not an easy read. It is for Kant experts only (cf. vol. i, p. 13), and only for those with a lot of time on their hands. Langthaler loves long and complicated sentences that pay attention to the subtleties and nuances of the German language (as the quotation above illustrates). An index of concepts would have made things easier, would have given readers the possibility to focus on isolated sections that stand on their own. Sometimes I had the impression that a clearer focus per section would have been useful; occasionally I got lost in a kind of maze. Every tiny detail of Kant’s train of thought is discussed (see for instance vol. ii, pp. 215–23 or pp. 230–5, a comparison with Schelling). Finally, I would have appreciated a historical contextualization in terms of the ‘existentialist’ perspective developed in the book.

The book is going to be a disappointment for all secularists among Kant interpreters: it is a massive and convincing argument for the viability of Kant’s critical philosophy of religion – offering the small ‘comfort’ for secularists that the inversion of Kant’s famous doctrine also holds true, that religion should lead to morality (vol. ii, pp. 342–63).