This is an excellent book. I was pleasantly surprised to read an innovative and stimulating analysis when I expected a rehearsal of familiar arguments. The authors manage to offer what they promise in the title, a profound commentary on one of Kant's most famous essays, and they shed new light on controversial issues.

The book is divided into two parts. The first one offers Kant's essay Toward Perpetual Peace (1795) and the relevant passages on the law of nations or international law in The Metaphysics of Morals (1797; cf. 7–87). The text is based on the Weischedel edition, and includes in the margin the pagination of this edition and that of the Akademieausgabe. The bulk of the book is a careful commentary by the two editors, offering a historical introduction, a step-by-step interpretation of the two texts, the history of the reception of Kant's texts, a section on Kant's legacy in contemporary debates, a glossary and an extensive bibliography.

The introduction sets forth the key thesis of the book: Perpetual Peace and the Doctrine of Right are seen as two complementary works which together offer a coherent system of international legal theory (cf. 98–9). Both works only seem to contradict each other; in fact they analyse and develop three distinct phases in the evolution of a global legal condition: the state of nature among states, a transitory phase and finally public international right (cf. 100–1 and 129).

After a historical introduction, which focuses, among other subjects, on colonialism and Kant's preliminary work, the authors continue with a profound analysis of the two texts, and this section is the longest part of the book (125–305). Based on their initial assumption that Kant distinguished three distinct phases in the evolution of a global legal condition, they divide this chapter into three sections, adding a fourth on Kant's reflections concerning the realization of this legal condition (usually subsumed under the title ‘philosophy of history’). I find this distinction particularly helpful and convincing. The first phase, the state of nature among individuals and nations and the corresponding natural law of nations (Völkernaturrecht) is the focus of several paragraphs in the Rechtslehre (§§53–60), and does not play a prominent role in the 1795 essay.

Eberl's and Niesen's methodological approach combines a historical contextualization with a step-by-step analysis of Kant's texts. The contextualization offers rewarding insights, from the possible influence of Achenwall (see for instance 153–4 and 163–4), Rousseau (184–5, 186, 244), Smith (187), the Federalists (245) and Vitoria (254–6) to political events like the crises of Poland in the 1790s (191–7) or the States General in The Hague (246 and 371). The textual exegesis is meticulous, for instance, when the authors discuss the concept of ‘representation’ in connection with the First Definitive Article (cf. 220–4).

This is really a commentary, which discusses in a fair way the different interpretations which have so far been offered, for instance §60 on the unjust enemy. The authors’ criticism sometimes becomes harsher when they hold that the interpretation is really at odds with Kant's explicit text or doctrine, as when they investigate whether Kant authorises the use of force to overcome the state of nature among states (cf. 172–3).

My criticism is minor. Unfortunately, the authors could not take into consideration (cf. 100) the recent book by Sharon Byrd and Joachim Hruschka: Kant's Doctrine of Right: A Commentary (Cambridge, 2010). This publication would have stimulated their discussion of the Third Definitive Article. Now it challenges their claim that cosmopolitan law is more than the postulate of free trade, namely a ‘right of communication’ (251). Byrd and Hruschka disagree and show that Kant's distinction among three forms of justice in a juridical state, the iustitia tutatrix, the iustitia commutativa and the iustitia distributive, offers the key to a different understanding of the law of world citizens. It refers to commutative justice, the public order for the market beyond state borders. According to Byrd and Hruschka, cosmopolitan law is nothing but ‘an ordered iustitia commutativa … on the international level in the absence of a iustitia tutatrix and a iustitia distributiva in a state of nation states’ (211). In addition, I would have liked an independent section on this very cosmopolitan law in the ‘Positionen der Forschung’; as it stands now, it covers the democratic peace proposition, the issue of humanitarian intervention and just war doctrines, and the problem of a world republic in contemporary debates. Current discourses on cosmopolitanism frequently refer to Kant's law of world citizens; it is the Definitive Article discussed most frequently at the moment. Finally, an index would have been helpful.

I want to finish on a personal note: all my books are mentioned and considered, which is really flattering. There was one thing I did not like when reading this commentary: I came to realize that my Pax Kantiana (1992) has become practically worthless and is now hopelessly outdated. Kant's essay, by contrast, will in all likelihood remain an attractive text, not the least because of its key strength, a ‘reflective perspective’ (104).