of politics is the theory of how to apply principles a priori. Kant’s theory of politics is a ‘doctrine of right put into practice’ (‘ausübende Rechtslehre’; VIII, 370, 11). Against Benjamin Constant, Kant asserts that no middle principle should be inserted between the principle of reason and its application.8 Politics may contain elements ‘drawn from experiential cognition of human beings’. In addition, pragmatic considerations are legitimate; politicians may ponder how to arrange the ‘mechanism for administering right’ (VIII, 429). The legal philosopher (who sets up principles) admits that the politician (who judges and applies) rules over a distinct domain. The legal philosophers, if they restrict themselves to their proper field, cannot know anything a priori about proper timing, historical circumstances or favourable conditions.9 As a legal philosopher, Kant claims that the principle of right should come first. All hypothetical maxims of politics are restricted by the categorical imperative of right. ‘Right must never be accommodated to politics, but politics must always be accommodated to right’ (VIII, 429).
Kant’s political thinking is evolutionary. Claudia Langer argues that some interpreters understood his political theory as a defence of the German Obrigkeitsstaat, the authoritarian (Prussian) state, only because they have overlooked that he favoured a reform according to rational principles.10 Peter Unruh claims that the respublica phaenomenon, the factual republic, is the scheme of the respublica noumenon within the framework of Kantian evolutionary politics. The Prussian monarchy is tolerated provisionally, for the time being. An absolute and peremptory condition of right is achieved by the rule of law ‘and depends on no particular person’ in a representative republic (VI, 341).11 Ingeborg Maus has emphasized the other cornerstone of Kant’s theory. According to Maus, Kant’s concept of popular sovereignty is procedural. The supreme legislative power has its legitimate origin in the united will of the people (VI, 313–14). The true republic is a representative democracy where popular sovereignty is restricted to legislation.12 In pre-republican, and thus pre-democratic, provisional states of affairs, the ruler has to resort to hypothetical universalization which is ‘in conformity with the spirit of a representative system’ (VIII, 352, 31). The ultimate goal is factual universalization in the law-making process. Maus sees a ‘Copernican turn’ towards ‘procedural natural right’ in Kant’s legal philosophy.13
This book tries to show how Kant’s attempt to mediate between a priori theory and practice works in the field of international law and relations. The above-mentioned authors focus on Kant’s state right and domestic affairs, and one might think that international relations are a different matter. However, Kant’s ‘application theory’ extends to international right as well. One striking example is given by the preliminary articles in Perpetual Peace, where Kant introduces permissive rights. Another example is a footnote in The Conflict of the Faculties (1798), where Kant argues that a monarchy like Prussia is entitled to keep its constitution in order to ‘maintain itself among powerful neighbors’ (VII, 86 footnote; see also chapter 1). A closer look at these aspects of Kantian international relations theory is the task of this book.
Some remarks on Kant’s system are necessary to avoid misunderstanding and confusion. What I have just referred to as Kantian international relations theory consists of two parts. On an empirical level, Kant analyses international relations. For example, Kant claims that ‘establishing a perfect civil constitution’ is dependent on foreign relations. The state of nature in international affairs has to be overcome if domestic justice is to be attained (VIII, 24). Kant also observes an interesting link between domestic and international affairs in eighteenth-century European states. He perceives that ‘civil freedom cannot very well be infringed without feeling the disadvantage of it in all trades, especially in commerce’. This in turn might reduce the power of the respective state ‘in its external relationships’ (VIII, 27–8).
On a normative level, Kant sets up legal a priori principles, which are not based on experience, custom, tradition, the common good or interests and so forth, but on what Kant calls practical reason and the innate right to external freedom. This reason provides a universal criterion which helps us to distinguish between what is right and what unjust. ‘Right is […] the sum of the conditions under which the choice of one (Willkür) can be united with the choice of another in accordance with a universal law of freedom’ (VI, 230, 24–6). This implies that rights are reciprocal; that human beings as persons are bearers of rights; that rules should govern the interrelations of persons.14 An example of a normative claim by Kant is that states have a legal duty (Rechtspflicht) to leave the state of nature and enter a civil condition (Rechtszustand). This duty cannot be deduced from the status quo or its observation. It is contained in the proposition that persons are entitled to the use of their external freedom. If – and this is Kant’s minimalist empirical assumption – humans cannot avoid having physical contact with each other (after all, the world is limited in space), then a civil condition must be instituted that secures their mutual rights and spheres of external freedom. Pure reason can tell us that much. It does not tell us precisely how this civil condition should look at the international level. This causes Kant a lot of trouble, as we shall see in the chapter on the federation of states. Kant’s or my own conclusions cannot claim to be based on pure a priori considerations (these are limited to the above-mentioned legal duty itself). Our conclusions, our attempts to specify this civil condition in detail, may be reasonable, but might not be rational in a strict sense.
I have outlined above how Kant’s application theory is the missing link between these principles and reality. Traditionally, Kant interpreters have assumed that this missing link was Kant’s philosophy of history. This is certainly not wrong, and my third chapter argues that the philosophy of history indeed tries to bridge the gap between ideal and reality. However, there is a systematic difference between applying principles for human beings who act (in politics, for instance), and the moral hope that reality, world politics or ‘nature’ will eventually also move towards a state of affairs where these principles rule.
This book is called Kant and the Theory and Practice of International Right. For Kant, the critique of reason investigates the sources and limits of our knowledge, and is an introduction (Propädeutik) to the system itself (III, 43, 10–12). The doctrine or ‘demonstrated theory’ builds upon the critique. The doctrine is the system based on a priori principles (analysed in the critique; IX, 14–15). Nowadays, Kant’s practical philosophy (including his political philosophy) is as highly regarded as his theoretical philosophy. This is an important development, since the more constructive side of Kant’s philosophy is to be found in his moral and political works. The main task of the Critique of Pure Reason is to clarify its concepts and to get rid of basic errors, and is thus predominantly ‘negative’ (III, 43). The moral and political writings, on the other hand, try to expand the scope of reason ‘for practical purposes’ (‘in praktischer Absicht’; V, 134–41; VIII, 18–19). Establishing principles of moral and political conduct is not negative, but constructive. Thus Kant’s normative theory of international relations, or his philosophy of international right, is part of what he calls ‘doctrine’. My argument is that Kant goes beyond his understanding of ‘critique’ and ‘doctrine’ as developed in the first Critique in his political and legal writings of the 1790s, by adding an additional element: the attempt to mediate between the doctrine and its application in practice.
Many interpreters have written about Kant and his ‘philosophy of peace’; most of their publications are essays. Interpretations by international lawyers are very rare. This book focuses exclusively on Kantian international relations theory; it does not treat it as a mere appendix to state right. I think this is one of the first full-length analyses of its kind in English. It faces many challenges. One of them is mentioned by Kant in his preface to The Metaphysics of Morals (1797). Kant admits that he has treated ‘some sections’ towards the end of the book less intensively than previous ones, above all because he thinks that these later sections can easily be deduced from the previous ones (VI, 209, 8–11). These later sections are those devoted to international and cosmopolitan right. The task of concluding from previous sections is certainly not an easy one. We can see this when Kant writes about analogies. For