Leibniz and European cosmopolitanism

Lukas K. Sosoe

Université du Luxembourg


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It might be surprising to many to present Leibniz as a political thinker, and more precisely, as one of the forerunners of a European cosmopolitan idea, that of European federalism. Leibniz is known as a great metaphysician, as well philosopher and diplomat, but not as a great political thinker of European and world scale. One need only choose the series of books dedicated to the history of Western political ideas to realize Leibniz’s absence. Not merely historians of modern European philosophy, but even political philosophers ignore Leibniz’s contribution to political philosophy, as a pioneer of the idea of the European Union. Leibniz’s name does not figure in German academic anthologies: absent, for example, from the fourth edition of the Klassiker des politischen Denkens (1979)1 from Plato to Max Weber, celebrated by the review Neue politische Literatur in the 70s as “ein gelungenes Schulwerk”, characterized by the book review the Zeit as a work expounding the “Gesamtbild einer Geschichte abendländicher Staatstheorie” and edited by political scientists like Hans Meier, Heinz Rausch and Horst Denzer. The chapter “The Federalists” of the same book mentions only the American founding fathers: Hamilton, Jefferson and other Federalists. No Europeans besides Immanuel Kant and the authors of the great idea of the Respublica Christiana of the Medieval and early Modern philosophy, are mentioned.

There may be many reasons for this. One of them owes to the huge volume of Leibniz’s philosophical work and the scattered character of most of his philosophical thinking, in addition to his status as a diplomat and politician, which overshadows his political philosophical writings. The separation of Leibniz’s political thought from his metaphysical theory stands as another reason. And finally, an important number of Leibniz’s political writings could be easily found in journals on the history of international relations or theology than in journals on philosophy.

The purpose of this contribution is to sketch Leibniz’s place in the history of political ideas on European federalism. We will not be able to give an exhaustive account of his political ideas in general, but we believe it to be possible to highlight his contribution to the idea of the European Union underlying the basic concepts of his political thought (Riley 1972, 1- 44), Goyard-Fabre, 1994, 105-120)2 by showing both the central role played by Leibniz in European political and federal thought as an important figure on the long list of the greatest pioneers of European federalism and the direct impact of his political ideas on great thinkers from Wolff to Kant and beyond.

In a word Leibniz proves as important as Crucé, Dubois, Guillaume Postel, Podebrady, Abbé de Saint-Pierre and even Wolff in his concern for a European federalism. With his program of a universal republic, Leibniz establishes himself as an important benchmark on the way to Wolff's universal republic and Kant’s Perpetual Peace.

In what follows, we will sketch in a first step Leibniz’s idea of a universal republic, which is a political ideal, also called by him, Optima Respublica or Respublica Christiana or Civitas Dei. Secondly, special attention will be paid to the theological and metaphysical foundations of Leibniz’s cosmopolitanism, to his Civitas Dei based on natural right embracing the whole world and to the place of the Christian republic within this cosmopolitan structure, i.e. a republic in accordance with the teachings of Jesus Christ. In this context, Leibniz’s Mars Christianissimus, which contains a very severe criticism of France’s imperialism in Europe and a defense of the German princes based on the Westphalian Treaty, plays a significant role. The last part will be dedicated to Leibniz’s position on European federalism and to his debate with Abbé de Saint-Pierre. This debate has the advantage to reveal clearly Leibniz’s idea of European federalism. It will become clear that these three parts are all based on Leibniz’s metaphysical and theological premises. This explains why many commentators of Leibniz’s political ideas contend that his whole metaphysics was at the service of his unified global international political order and, specifically, at the service of his Civitas Dei. (Cheneval 2002, p. 53)3


Leibniz’s political thought can be summarized thusly: harmony and reconciliation and conciliation. Without the search for harmony and conciliation, Leibniz’s philosophy would amount to that which Bertrand Russell takes it to be: a sheer opportunistic discourse at the service of changing European political powers. (Rusell 1964, p. 202)4 Through harmony and conciliation, Leibniz succeeds in laying down the metaphysical and theological foundation of the unity of this thought made of “apparent conflicting ideas” taking from each kind of thought that which proves soundest and synthesizing it with the seemingly incommensurable truths of other systems, in this way fusing “Platonism, Cartesianism, Christian voluntarism, Hobbesian mechanism”, etc., into a system of thought. (Riley, 1972, p. 2)5 That is why the search for the “harmonie universelle” or universal harmony is the key concept which lends Leibniz’s philosophy a unified shape and can be seen as the core of his thought. (Holz 1996, p. 5)6 One understands why Leibniz sought to develop a universal jurisprudence. By “universal jurisprudence”, we mean that Leibniz intended the establishment of a world republic, a hierarchical system of law common to God as the perfect being and man. “God and man exist in a society of a universal republic of spirits, the noblest part of the universe […] in which universal right is the same for God and for men.” (Riley 1972, idem)7 The cosmological and cosmopolitan character of Leibniz's political philosophy appears from the start. It stands as a metaphysical theory based on God and the order of creation.

Leibniz welcomes every idea necessary to sustain this political philosophical program. One of the best illustrations is his work: Civitas Dei, the City of God where God is considered the supreme power, the monarch. Since God is the monarch of the universal city, his word is the natural law and theology a part of jurisprudence. The Christian Church hence possesses a legal and political significance. Whereas believers or Christians are the citizens of God’s Republic (Republica Dei), pagans are declared rebels who must be fought (ubi infideles quasi rebelles sunt). (Leibniz 1666, par 42, p.190)8 In this political theory of universal monarchy, morality can only be understood as a legal concept and the relation between man and God as a political relation hierarchically ordained. That is why for Leibniz “it is best to derive human justice, as from a spring, from the divine in order to make it complete. Surely the idea of just, no less that the idea of the true and the good, relates to God. (...) and the rules which are common certainly enter in to the sciences and ought to be considered in universal jurisprudence.” (Leibniz, 1706)9

Leibniz's metaphysics is entirely written in political concepts. It appears from the above cited text that there is no difference between God’s and human justice. The difference proves one of degree. It can be considered on three levels: 1) On the level of the relation between Man and God, 2) on the level of the natural law of the entire human race and 3) on the level of the State.

The State, according to Leibniz, represents the lowest stage of the universal legal public order. It is subordinated to the World and the human race. Leibniz speaks of “omnia societati universali sub Rectore Deo” instead of the World, and this reveals the cosmological and cosmopolitan character of his conception of Law. That means that the whole world is God’s city and the legal rules of this city his Laws.

Secondly, the metaphysically grounded structure of Law has a goal, namely the common good (publice utile), because it is subordinated to the direction of God’s will insofar as God as Monarch of the whole universe wants for Man the best possible good.

Thirdly, when Leibniz refers the State to the universal structure of Law, he does not heed the fate and the multiplicity of concrete States. For him, individuals do not matter in this context. The fact of their existence is neglected or underestimated when compared to the world legal divine order. The project of the Civitas Dei or of the universal cosmopolitan republic prevails over the individual States in which God is the Sovereign and legislator. Leibniz is convinced “que le monde est une espèce de cité aussi bien ordonné(e) que possible, dont le Seigneur a en main la sagesse et la puissance souveraine”(Leibniz 1679, p. 523) 10 for the common good of the spirits. By spirits, Leibniz means all reasonable beings, all monads or simple substances living in the City where God reigns as Monarch. The Civitas Dei is a society created, conserved and governed by God. It proves a cosmopolitan State based on reason. As Leibniz states it in the Discours de métaphysique:

Il ne faut pas seulement considérer Dieu comme le principe et la cause de toutes les substances et de tous les Estres, mais encore comme chef de toutes les personnes ou substances intelligentes, et comme Monarque absolu de la plus parfaite cité ou République, telle qu’elle est, celle de l’univers composée de tous les esprits ensemble, Dieu lui-même étant aussi bien le plus accompli de tous les Esprits.”11 (Leibniz 1686 par 35, 88)

In these, one finds the main lines of Leibniz’s political philosophy which can then easily be summarized by underlining the Civitas Dei's main characteristics. The Civitas Dei is metaphysical-theologically conceived as the normative ideal of the perfect State and Monarch, the latter God himself. All human beings and societies have to submit themselves to this Monarch's power, which is not to be identified with command but with justice. Every rational being necessarily belongs as citizen to the City of God. We have also mentioned the City's cosmopolitan nature. The main question is how and where Leibniz’s European federal order fits in this overarching world society. Where is the place of a federal Europe in the world political structure and which kind of role does Leibniz assign Europe to play therein? And, finally, as the whole political philosophy is based on God, what is the function of religion and, specifically, the Christian religion in world politics and in relation to non-Christians in the world?


Leibniz’s political philosophy cannot be thoroughly presented without mentioning his writings on international relations, especially the relations between European states. For that, we need to know more of Leibniz's conception of natural right.

In writing on international affairs, Leibniz gives a concise definition of natural right and the relation between natural right, Civitas Dei and international Law.

In a paper on Abbé de Saint-Pierre's project of perpetual peace in Europe, Leibniz writes:

When I was quite young, I became acquainted with a book entitled Le Nouveau Cynée whose unknown author advised sovereigns to govern their states in peace, and to let disputes be judged by an established tribunal, but I no longer know how to find this book…” (Leibniz 1715, Riley 1972, p.178-183)12

This indicates his early interests for European and world political problems given that the book Le nouveau Cynée speaks of peace and unity in Europe, which Leibniz's Codex Juris Gentium (Leibniz 1693; Riley, 1972, p.165-176)13 will further develop.

Contrary to almost all philosophers in his lifetime, Leibniz shows in the definition of political philosophy's main categories that there proves no separation or distinction between Law, religion and theology. “Tout est lié”, he contends, not only in the City of God but also in international relations, the ultimate ends of which remain peace and happiness for the realization of which Europe possesses a special mission.

One of the objectives of the Codex Juris Gentium is, as stated in the Preface, to understand the law of nations. Nevertheless, Leibniz takes the opportunity to clarify again a few basic notions from his political philosophy like justice and law, which, Leibniz laments, even after having been treated by so many illustrious authors, have not been made sufficiently clear.14

“Right is a kind of moral possibility and obligation a moral necessity. By moral, I mean that which is equivalent to “natural” for a good man [...] A good man is one who loves everybody, in so far as reason permits [...] Justice, then is, [...] will be most conveniently defined […] as the charity of the wise man, that is charity which follows the dictates of wisdom” (CJG, 170-171).

Needless to say how strange and peculiar these definitions are compared to Hobbes' or Pufendorf's and even to Grotius'. Leibniz’s definition has little to do with the natural right tradition. The reader will already have noticed it with the main features of the Civitas Dei. Most of Leibniz's writings make no difference between law, a legal duty and a moral duty. Here begin the difficulties in understanding Leibniz's concepts of practical philosophy. Far from Locke's distinguishing two great maxims in moral philosophy, namely justice and charity, Leibniz's conflation of the two comes out in the following definition: “Charity is universal benevolence and benevolence the habit of loving or willing the good. Love signifies rejoicing in the happiness of another [...] into one’s own.” (Idem) At first glance, the reader is drawn into utilitarian considerations. Then, as D’Holbach says: “L’homme vertueux est celui dont les actions tendent constamment au bien-être de ses semblables. La vertu n’est que l’art de se rendre heureux soi-même de la félicité des autres.”(D’Holbach 1966, Chap. XVI, p. 405) 15 Yet Leibniz’s conception of happiness ends at a theological idea of God’s perfection, an idea which no utilitarian would defend. Thus Leibniz says that divine love exceeds all other loves because God can be loved with greater result since nothing is happier than God and nothing more beautiful and more worthy can be conceived.” (CJG, 171) Leibniz contends that, as God possesses the supreme power and supreme wisdom, his happiness becomes and even creates our own. At last, he concludes that wisdom is the science of happiness.

The clearness of this chain of definitions proves far from self-evident. This is not, however, the place to analyze in detail the relationships between wisdom, happiness, benevolence, perfection, utility and charity. All these concepts lead to Leibniz’s conception of law and justice; the latter is the Love of God from which natural right flows. Furthermore, simple right is born out of the principle of conservation of peace. This stands as the principle of avoidance of misery, and higher right tends toward happiness. But to prove the truth of this conceptual edifice, Leibniz contends, we must assume the immortality of the soul and the existence of God as ruler of the universe, a perfect monarch who imposes all natural laws, rewards just actions and punishes wrong ones. “The divine providence and power cause all right to become fact and assure that no one is injured except by himself, that no good action goes unrewarded, and no sin unpunished.” (CJG, 174) Indeed, this is the teaching of Jesus Christ.

Leibniz’s definition of natural law follows from theological grounds. Accordingly, it leads us to a universal political order based on divine providence. Although it also contains the description and analysis of the political situation in Europe, such as the alliances and treaties between princes, the Codex Juris gentium, at least in its preface, proposes little more than the description and explanation of divine monarchy. On this ground, justice is called universal and includes all other virtues, even duties towards oneself, such as “not to abuse our own body or our own property”. These kinds of abuses, which stand beyond the power of human laws, “are still prohibited by natural law, that is the eternal law of divine monarchy, since we owe ourselves and everything we have to God.” (CJG, 174) It appears that without God’s supreme power directing the universe, punishing wrongs and rewarding good actions, there can be no moral and political order. Leibniz establishes this order on a theologically founded natural right theory which is of interest to the state and of a much greater interest to the universe. (CJG, idem)

All that is needed for the development of cosmopolitism has already been given. And Leibniz’s theologically, even christologically founded cosmopolitism serves as a theoretical realm in which European federalism finds its legitimate place. Before we come back to this topic, a few more stories need to be told on Leibniz’s international relations or divine monarchy.


Leibniz takes it for granted that the Christian religion reveals God’s will and should likewise be the fount of the world social and political order, as much of the individual states as of European federalism. The tight link between the City of God, the theory of natural right, and revelation gives the impression that Leibniz’s political thought finds its ground in a kind of theology of revelation. This would mean that the ultimate justification of the Divine city rests on faith in the teachings of Christ and the Christian religion. At this point, there becomes necessary further clarification which we cannot undertake here. Nonetheless, it should be noted that Leibniz confers, without any justification, a precedence to Christianity over other world religions and justifies its extension through war against those religions and cultures in the world as we will see later. For present purposes, it suffices to bring forward a few passages to show the kind of dogmatic certainty with which Leibniz affirms the so-called truths of the Christian religion and their superiority over other religions:

“Les anciens philosophes ont fort peu connu ces importantes vérités : Jésus Christ seul les a divinement exprimées et d’une manière si claire et si familière que les esprits les plus grossiers les ont conçues [...] il nous a donné à connaître le royaume des cieux ou cette parfaite république des esprits qui mérite le titre de cité de Dieu et dont il nous a découvert les admirables lois.”(Leibnitz 1686, Ed. Fichant 2004)16

Jesus Christ’s teaching not only overrides that of other religions. For Leibniz, there is no doubt that Jesus stands as the founder of the purest and most enlightened religion:

“les sages d’autres nations en ont peut-être autant quelquefois, mais ils n’ont pas eu le bonheur de se faire suivre assez et de faire passer le dogme en loi [...] jusqu’à ce que Jésus Christ leva le voile, et sans avoir la force en main, enseigna avec toute la force d’un législateur que les âmes immortelles passent dans une autre vie, où elles doivent recevoir le salaire de leurs actions [...] Jésus Christ acheva de faire passer la religion naturelle en loi, et de lui donner l’autorité d’un dogme public.”(Leibniz 1710, Ed. J. Brunschwig 1969)17

This finds its basis in what here seems a revelation as Leibniz observed that the theory of natural right is “jus naturae et gentium traditum secundum disciplinam chriatianorum id ex Chriti documentis” (CJG, p.8)18 and that “the learned have rightly held [...] that the law of nature and of the nations should follow the teachings of Christianity [...] the divine things of the wise, according to the teaching of Christ.” (CJG, p. 174)

Besides the concept of natural right so defined, Leibniz also recognizes what he calls voluntary right “derived from custom or made by superior”; in the state, civil law receives its force from the one who holds the supreme power. Outside the state, the supreme power is the voluntary law of nations originating from the tacit consent of peoples. In addition to this international law of nations, Leibniz contends that “Christians have another common tie, the divine positive law contained in the sacred Scriptures [...] the sacred canons accepted in the whole Church and, later, in the West, the pontifical legislation to which kings and peoples submit themselves.” (CJG, id.) This Christian universalism overshadows the rational structure of other peoples' natural right and allows Leibniz to restrict his cosmopolitism to European Christian nations, to the “common republic of Christian nations”, the heads of which remain the Pope in sacred matters and the emperor in temporal matters. Thus, Leibniz's cosmopolitism ends at a Europeanism in which two different theories are at play: one is rational and general and valid for all; the second based on positive legal structure derived from Christian revelation, gentium christianarum respublica, in other words, a Christian republic which is, at the same time, for Leibniz, the justification of the European Christian federal order with the right to wage wars against non-Christian peoples, Turks, Muslims and non-European peoples. The question proves how this Europeanism can be situated, “harmonized” or “conciliated” within Leibniz’s universal political theory, i.e. in Leibniz's cosmopolitanism.

A partial and tentative answer to this question may be found in the Codex Juris gentium where Leibniz develops his conception of war and peace. It may help 1) in understanding why and how Leibniz's universal republic can go hand in hand with his strong Europeanism or European federalism and 2) in capturing its fundamental intuition.

Leibniz deems it not unreasonable to believe, like Hobbes, that war between states and peoples is and will be perpetual. Wars are destructive and do not honour the belligerents, most of all a war waged between civilized nations. In this sense, Louis XIV's expansionist politics in Europe should be severely condemned. Leibniz himself did so in his Mars Christianissimus. Leibniz is not, however, a pacifist for maintaining such. Indeed, it is preferable that the state be ready for war if needed or that they make tactical alliances against an assault coming from an enemy. Thus, it remains prudent and realistic to ready oneself, for, as Leibniz writes:

“Quand les Français prêchent la paix, c’est à peu près le sermon que le renard allant en pèlerinage à Saint Jacques et publiant une amnistie générale entre les animaux, faisait à une troupe de poules qu’il rencontra sur son chemin. Ils ont sans doute fort bonne grâce de parler de paix perpétuelle, eux qui ne connaissent aucune autre que celle d’un esclavage générale à la turque.”(Leibniz, Werke 1864-1884)19

Nevertheless, Leibniz insists on the validity of a minimal justice demanding that one not injure anyone, of a superior justice corresponding to charity, and of a universal justice useful for all mankind. Yet the validity of the rules of justice does not stand in opposition to the idea that, if one wants peace, one should be ready for war. “Tout home de bien, says Leibniz, demeure d’accord qu’on ne doit jamais faire guerre que lorsqu’il est nécessaire” (1864-1884, 110) Therefore, states which follow peace should be armed, unless they are united by common interest. In that case they must make alliances with each other. Against France’s expansion the just war is that which the just man should undertake to restore peace. (1625, Truyol y Serra 1984, p. 68)20


The political situation in Europe after the Thirty Years War was one of total desolation, misery, hunger and political anarchy. In this situation, which kind of peace there was for reconstruction? With a common interest in both, European states needed more than ever to become closer and work together. As a Christian philosopher, jurist and diplomat, Leibniz felt the necessity to take concrete measures for the reconstruction of Europe: 1) reconstruction of Christianity's lost unity, 2) reconstruction by pacification of political relations between European countries by exporting the violence outside Europe and 3) construction of the project of a European union.

1.) Leibniz never accepted the Church's division following the Reformation. As one can notice in his correspondence with Bossuet, he strives for the unity of Catholic and Protestants by downplaying insofar as possible the dogmatic aspects of the church's division and by putting his effort into the unity of Christianity and the integrity of the Holy Roman Empire's constitutive nations with the Pope and the Emperor as the spiritual and secular heads respectively. But numerous tensions and rivalries plagued the empire. Accordingly, the solution lay in exporting tensions and wars outside Europe; its states, for the sake of peace, should then conquer other parts of the world in order, among other ends, to spread the Christian religion and, at the same time, to satisfy their thirst for power and expansion.

2.) Indeed, Leibniz makes concrete proposals about the way political structures in a 17th century Christian Europe devastated by wars could reorganize themselves through the imposition of the pax christiana on the world. Starting with the acknowledgement of an imbalance between forces at the European level, Leibniz made every effort possible to analyze methodically the situation and, to that end, made suggestions, where his diplomatic talents constantly shone through. Through metaphysically and religiously based argument, he legitimates France's conquest of Egypt, and this not without defending the Habsburgs against France. In a highly satirical and somewhat amusing writing, Mars Christianissimus (Most Christian War God, 1683), he suggests that France wage war against the Turks instead of conquering Christian nations like Holland and other European nations. In this same writing, Leibniz voices the idea of an alliance between German Protestant princes against the power of Catholic France under Louis XIV. And beyond Louis XIV, he pleads for a new European political balance. For Leibniz, the political unbalance in Europe owes to the “House of France”, to which the Peace of Westphalia (1648) and the Treaty of the Pyrenees (1659) have granted too many advantages. These treaties, intended to protect stability in Europe or the “political balance of Europe”, have instead led to a state of disharmony that fails to respect other states’ sovereignty. According to Leibniz, the “policy of balance” proves in fact a policy that is “unbalanced”21. Before this balance, it is important to rethink the overall issue of interstate relationships, to replace, on one hand, strategies of division by those of unity and, on the other, strategies dictated by passion by those of reason.

Leibniz's solution consists in “exporting” the tensions and rivalries between European houses to other parts of the world. The justification of this imperialistic solution lies in the superiority of the European Christian religion and culture. First of all, Leibniz recommends to Louis XIV to conquer Egypt; by doing so, he will strengthen his kingdom and weaken the Turk instead of waging war against Holland, a Christian country:

“Je veux parler, Sire, de la conquête de l’Egypte. De toutes les contrées du globe, l’Egypte est la mieux située pour acquérir l’empire du monde et des mers : la population dont elle est susceptible, et son incroyable fertilité, l’appellent à cette élévation. Jadis, mère des sciences et sanctuaire des prodiges de la nature, aujourd’hui elle est le repaire de la perfidie mahométane, pourquoi faut-il que les chrétiens aient perdu cette terre sanctifiée, lien de l’Asie et de l’Afrique, digue interposée entre la mer Rouge et la Méditerranée, grenier de l’Orient, entrepôt des trésors de l’Europe et de l’Inde?”(Leibniz, 1672 Ed. de Joffmanns 1840)22

Leibniz finds two justifications for Egypt’s conquest. The first consists in hindering France’s expansion wars in Europe. The second reason lies in spreading the pax christinana all over the world.(Kaplan 1995 p. 91.95)23 The conquest of Egypt is a “bellum sacrum”, a holy war against the pagans for the utility of mankind. Economically and politically, Europe's greatest threat, the Turks, will be discarded. By giving up its expansion in favor of the Christian nations and by waging war against the infidels, France and the Habsburgs will share mastery of the world and will be able to contribute both to the Christian religion's expansion and to peace and prosperity in Europe.

3.) In a third step, Leibniz designs a project for political Union for the prosperity of Europe, although he himself favoured universal monarchy. At the time, he still admired Louis XIV and would have entrusted him with the general direction of European state affairs: at the least, the charge of arbitrating disputes and litigations. When confronted, however, with Louis XIV's expansionist politics, wholly at odds with a politics of concordat, he gave up his first draft of the project of the Union and concentrated his effort on German unification. For Leibniz, Germany “is the kernel of Europe” (CJG, § 87). Leibniz further wrote in a strong nationalist mood that there is only Germany which is “personne civile” (CJG, §88) capable of giving Europe its unity. It therefore proves vital that it become a highly centralized State. It must become a true federal State legally harmonizing or conciliating the diversity of German states in political unity: the Empire.

In his capacity as diplomat and also philosopher, Leibniz suggests to each power a solution to satisfy its thirst for expansion in the world. To Leibniz, that division amounts to what those powers must do to ensure peace in Europe: the carving up of the world outside Europe. Thus. England and Denmark have to occupy North America; Spain, South America; Holland, East Indies; and France, with divine providence, is designated as the Christian warrior in the Middle East. To that end, it finds itself bound to attack Africa and Egypt. Likewise, West and East India must be dominated. Human beings must wage war against wolves and wild animals prior to domestication, to which barbarians and infidels are likened.24

It is only at this price that Europe can realize its dream of peace. At the same time, Leibniz develops a cultural plan consisting in the creation of learned societies to help to complete his imperialistic program. For peace and development and all the interests of mankind, learned Societies are indispensable to achieving the ideal of Civitas Dei. In this sense, Leibniz fully shares the scientific optimism of Bacon’s Novum Organum.

As Goyard-Fabre expresses it, “to rebuild Europe’s shredded political unity, is a task that, in Leibniz’s philosophy, does not come under the classic issue of 'The One and the Multiple'; it must be considered metaphysically, that is to say according to the vertical reference to the almighty divine’s eminent perfection of which universal harmony and jurisprudence are the expression”. (Goyard-Fabre 2011, p. 41)25 This implies the transformation of the circumstances of justice, imposed by the House of France, to use Hume’s expression, into circumstances of peace, based on law – law offering possibilities of regulation outside of the state of non-right, the state of nature. But law means understanding, and understanding means that we are only one step away from establishing its mechanisms: a union of all European states. Then what stands as the basis of the union recommended by Leibniz?

In his work Securitas publica, impressive as it remains relevant even today, Leibniz suggests an association of sovereigns (§32), presided by a rotative Emperor, its objective being a “permanent alliance” (concilium perpetuum) with the function of the arbitration in order to avoid an absolutist government. That is why a federation of sovereign national states would be the suitable political strategy. The federation of sovereign states will assure the political unity necessary; every state needs to defend its interests against other political powers but also to respect the freedom and plurality of the States under the imperial administration. This kind of federation of national sovereign states is far from what Abbé de Saint-Pierre is proposing which is totally different from the perpetual council aiming at “the common interest of States” (§24)26 in the same Empire. Thus introducing a theme which he discussed unsuccessfully with Abbé de Saint-Pierre, Leibniz insists on the creation of peace in the union, on the safeguard of each people's and culture's difference. The advocated union must, at the same time, guarantee the diversity of its components. With this, he anticipates by two to three hundred years the “aborted” project of a European constitution wherein the question of unity in diversity is raised (Oliver Duhamel, 2003, p.158) 27 - which, unfortunately, is no longer to be found in the Lisbon Treaty. Far from being an obstacle, that diversity is well accepted and perceived and remains, to Leibniz, the stepping stone towards the opening up of other sociopolitical and cultural horizons: towards the cultural wealth of each state, each nation having its own particular genius.


One cannot entirely discuss Leibniz’s foundation of European federalism without taking into account the correspondence between l’Abbé de Saint- Pierre and Leibniz about the Mémoire pour rendre la paix perpétuelle en Europe (1712), which helps him to clarify some points of his European federal dream. Leibniz cannot be indifferent to that project. Vanishing though his dream is to resuscitate the Holy Roman Empire with the Pope and the Emperor as heads of the Empire of universal Christendom, he answered Abbé de Saint-Pierre. His answer reveals how realistic and practical Leibniz could be in political matters but also his position against the federation of individual sovereign States based on a contractual model.

L’Abbé de Saint-Pierre published from 1712-1717 his Projet de paix perpétuelle wherein he puts forth an idea of European Union founded on the contractual tradition. This intends to replace the imperial order by a federation of sovereign states with a central government. This project of a Union bases itself on a dual political power, the major goal of which is to secure peace in Europe, as indicated by the title. He sent it to Leibniz not only to seek his opinion but to use his influence to help the former convince European princes.

In his first reaction to Saint-Pierre, Leibniz expresses an apparent scepticism full of civility. But, as we know, his theory lies in imperial Christian order. “Men lack the will to deliver themselves from an infinity of evils”, he wrote to Abbé de Saint-Pierre: “If five or six persons wanted to, they could end the great schism in the West and put the church in good order” (Leibniz, 1715 Ed. Riley, 1972)28 To put an end to wars, “it would be necessary that Henri IV, together with some great princes favour your project. The evil is that it is difficult to suggest it to great princes.” (Leibniz 1715, idem)29

But this finds itself only the apparent reason. Indeed, the main reason proves that, in his Codex Juris gentium, Leibniz carried out a general inventory and evaluation of international relations and all agreements made under the history of the Empire. This history is, for Leibniz, the princes' concrete rights, especially those of the Holy Roman Empire's princes. (Cheneval 2002, p. 112-113)30 It amounts to more than a merely normative discourse like the Saint-Pierre’s project, which remains, for Leibniz, wholly cut off from concrete legal life and historical reality, from the psychological and strategic considerations of European princes.

In a small text, “Observation on the Abbé de Saint-Pierre’s project for perpetual peace” written in 1715, Leibniz insists on the fact that Saint-Pierre’s project has no originality. Leibniz shows clearly his position by questioning the project's originality in reference to Crucé’s Cyneas.31 Leibniz maintains his position against Saint-Pierre’s idea of confederation. For him, Saint-Pierre’s project of perpetual peace is somehow naïve. The European political situation does not allow to see any dream of perpetual peace. The project is a utopia the political price of which would be very high. It will lead to the lost of freedom, happiness and justice of the citizens and each confederate member state will follow its own economic and politic interests and lose sight of the common ones which can be favored only by the Empire of the German principalities the union of which is indispensable for a new equilibrium in Europe.

With his Realpolitik Leibniz thinks that Saint-Pierre’s project is against the very idea of international law and international politics. In his opinion a Saint-Pierre’s project of European federation transgresses the idea of international politics understood as a legitimate “struggle for power” to survive and safeguard one’s sovereignty. Unless the sovereignty of other States is guaranteed, the achievement of a confederation would not be only totally irrational, but also an impossibility in a state of total disequilibrium, devastation and desolation. In any case, it would not be the best action to be taken.

For Leibniz, the European federal state has to avoid absolutism. It must contribute to the rise of a strong nation indispensable for political equilibrium in Europe. It must be powerful enough to oppose the two potential aggressors, from the East Louis XIV’s France and from the South the Muslim Ottoman Empire. For that a treaty is needed between different nations of the Empire if the search for equilibrium must become a reality, a real peace depending on that equilibrium if we don’t want to confuse the Pax Ludovica or the French peace with that which Europe really needs.

Leibniz’s position is not only similar to a Hobbesian account of security in the natural condition of man but also to the contemporary security solution adopted during the cold war in Europe. The dictate of reason in Hobbes’s natural condition of man is “that every man, ought to endeavor peace, as far as he has hope to obtaining it; and when he cannot obtain it, that he may seek, and use all helps and advantages of war”. (Hobbes, Leviathan 1976, Chap. VIV, p.190)32 Leibniz is also for peace but not any price and at any condition. It seems to him that the most rational course of action in the situation in which the German states find themselves at that time, needs war to restore acceptable, that means fair conditions of peace. It is also the kind of action taken during the cold war : the balance of terror. Only a good balance of terror has produced a deterrence effect on the world power. Without the Union of the states of the Holy German Empire there can be no peace or the only peace possible would that of the House of France. So Saint-Pierre Project would suppress one side of the scale. And this against the idea of Harmony. That is why is necessary to restore, even at the price of war, the precondition of peace: political equilibrium of European political powers.

Leibniz’s concept of peace is very different from that of Kant. Peace is a negative concept for Leibniz. It means the absence of war (pax absentia belli) and is contingent treaties (pactum pacis) among states or parties and achievable only through an international legal order (jus Gentium) which confers its legitimacy to the just war against the infidels, non-European, especially Turks and perhaps France (Bellum justum) (Rodan, 2007 p.124)33

Should the federation be absolutely realized, the unity of the Empire should be conserved as a member of the confederation.

“Since Saint-Pierre has given us two plans for Christian society, Leibniz argues, one in which the Emperor with the Empire make up one member and one in which the Empire is destroyed and in which the emperor would have a voice only as a hereditary sovereign (in Austria) and in which the elector would have each one vote, I must be for the former plan and Justice itself would prefer this plan, following the very principle of M. l’Abbé de Saint-Pierre, that the Christian society must leave things in their present state.” (Leibniz 1715, Ed, Riley 1972, p. 181)34

Should the federation be inevitable, the Empire must remain as it is. Otherwise, Leibniz goes quite far in the direction of Saint-Pierre’s Project, which he apparently took rather seriously as a diplomat and as a politician. As regards Saint-Pierre's proposal of a European tribunal, Leibniz observed that it possesses no guaranty. Perpetual peace between States requires a guaranty without which any agreement would prove mere words for powerful princes. He took up the European confederation's fourth article, which provides for administrative and even military sanctions against member States unwilling or unable to comply with the rules. This article in Saint-Pierre’s project reads:

“By the fourth shall be specified the conditions under which any Confederate who may break this Treaty shall be put to the ban of Europe and proscribed as a public enemy: namely, if he shall have refused to execute the decisions of the Grand Alliance, if he shall have made preparations for war, if he shall have made a treaty hostile to the ends of the Federation, if he shall have taken up arms to resist it or to attack any one of the confederate.” (Rousseau, 2013, p. 574) 35

Instead of planning to declare war against the State inclined to violate the federal clauses, Leibniz makes the proposal to establish a European Federal Court in Rome over which the Pope should preside and play judge between Christian princes. He pleads for resuming the old ecclesiastic authority, as well as for excommunication “making Kings and Kingdoms tremble”. Similarly, he stands for a federal financial guaranty, for an European central Bank, because certain nations will be powerful enough not to respect the European tribunal. Thus, to reinforce Saint-Pierre’s proposal, he wrote:

“It will be necessary that all these gentlemen contribute a caution bourgeoise or a deposit in the bank of tribunal, a King of France, for example, hundred millions écus and a King of Great Britain in proportion, so that the sentence of the tribunal could be executed on their money, in case they prove refractory.”(Leibniz 1712 Ed. Riley 183-184)36

The interest of the guaranty would be returned to the princes; in cases of refraction, the princes would, however, lose them.

Both contrary to Kant’s hyper-optimistic and somewhat metaphysical solution, wherein the reference to providence or nature replaces the guaranty of perpetual peace, and against Saint-Pierre’s proposal of judicial sanctions without the power of enforcement against powerful member states, Leibniz suggests a highly practical and pragmatic solution two years before his death. Leibniz’s suggestion is a politician’s diplomatic decision, a strategic decision. Leibniz neither waits for nature’s prowess to drive human beings willy-nilly to peace nor for a punitive expedition of tribunal doomed to failure in the face of powerful states. Leibniz chooses the path of efficiency: a European central bank, as the use of force or war remains uncertain in terms of time and resources. For Leibniz, a financially backed agreement comes to the best guaranty of peace.

Although Leibniz sends this letter to Saint-Pierre to show his good will to review the project, he still believes it rather unoriginal and classifies it on a long list of similar proposals. For Leibniz, it stands as one more project among many others on peace in Europe; yet it proves nothing but a romance. “But since it is permitted to write romances,” he confesses in the same letter to Grimarest, “why should we find bad the fiction which would recall the age of gold for us.”


A history of transcendental philosophy without Kant would be not imaginable. It is not exaggerated to say that the same holds for Leibniz concerning the philosophical foundation of the European Union. No account on the philosophical foundation of European federalism will be finished without mentioning Leibniz’s philosophical endeavor. At quite different periods of his life, Leibniz seeks solutions as to how Europe's unity could be achieved through a union or a federal system. From the metaphysically grounded ideal of Civitas Dei to the Letter to Grimarest about Saint-Pierre’s project two years before his death, Leibniz never ceases to insist on European unity in his writing. He finds in this unity the ferment for the development of the whole world and human emancipation. Peace is needed for that. And, for Leibniz, it will come from Europe. Yet still Leibniz remains a cosmopolitan philosopher. His Eurocentric attitude has to be considered as a stage on the way to a world society even if, from a normative point of view, it remains unacceptable. It is not an end in itself but just as his argument for just war one of the means to a global political order, the last stage of which will be dominated by learned societies. In this sense, a more systematic contribution will certainly be necessary to account for the many, sometimes contradictory, aspects, of Leibniz’s immense legacy in political philosophy in general and especially for Europe, an Europe contributing to peace and harmony in the world.


I. Leibniz. Quoted publications

Leibniz, Discours de métaphysique, édition établie, présentées et annotée par Michel Fichant, Gallimard, Folio, 2004.

Leibniz, Codex Juris Gentium (CJG) (1693) ed. Paul Riley: Leibniz. Political Writings, Cambrigde University Press, Cambridge, 1972.

Leibniz (1864-1884) Die Werke von Leibniz. Historisch-politische und staatswissenschaftliche Schriften, Hanover , vol V.

Leibniz (1670-1671) Bedenken , welcher Gestalt secruritas publica interna et externa und status praessens im Reich iezigen Umbeständen nach auf festem Fuß z stellen, in Gottfried Wilhelm Leibniz, Sämtliche Schriften und Briefe, ed. Paul Ritter, Darmstadt, Preussische Akademie der Wissenschaften, 1923.

Leibniz (1706) Opinion of the Principles of Pufendorf , ed. Riley, Leibniz. Political Writings, Op.cit.

Leibniz (1715) Letter II to Grimarest: Passages concerning the Abbé de Saint-Pierre’s Project of Perpetual Peace (June 1712). This proposal will be sent to Abbé de Saint-Pierre on the 4th of April 1715 by Leibniz himself.

Leibniz (1715) Observations sur le projet de l’Abbé de saint Pierre, ed. Riley, Op. cit.

Leibniz (1840) Mémoire de Leibniz à Louis XIV, sur la conquête de l’Egypte, ed. By M. De Hoffmanns, Edouard Garnot, Paris.

Leibniz (1625) Leibniz, Raison touchant à la guerre ou l’accomodement avec la France, in : Klopp, Gottfried Wilhelm Leibniz : Historisch-politische staatwissenschaftliche Schriften, V, 1868-1884.

II. Secondary literature

Russell, Bertrand (1964) A Critical Exposition of the Philosophy of Leibniz, Allen, London.

Cheneval, Francis (2002) , Philosophie in weltbürgerlicher Bedeutung. Über die Entstehung und die philosophischen Grundlagen des supranationalen und kosmopolitischen Denkens der Moderne, Schwabe Verlag, Basel.

Duhamel, Olivier (2003), Pour l’Europe. Le texte integral de la constitution expliqué et commenté, Seuil, Paris.

Goyard Fabre, Simone (1994) La Construction de la paix ou le travail de Sisyphe, Vrin, Paris, 1994.

Goyard-Fabre, Simone (2011) “L’européanisme des pionniers” in: Regards croisés sur la constitution avortée de l’UE, in: Gary Overvold, Philippe Poirier et Lukas Sosoe (Ed.) Paris.

Hobbes, Thomas (1976) Leviathan, Penguin, London.

D’Holbach (1966) Le système de la nature, Hildesheim, New York, 1966.

Holz, Hans Heinz (1996) Sitzungsberichte der Leibniz-Sozietät, 13.

Kaplan, J. Zenz (1995) Das Naturrecht und die Idee des ewigen Friedens, Brockmeyer, Dortmunder Historische Studien.

Klassiker des politischen Denkens (1976) Vol. I. Von Plato bis Hobbes; Vol. II Von Locke bis Weber, ed. Hans Meier, Heinz Rausch and Horst Denzer Munich.

Regards croisés sur la constitution avortée de l’UE (2011) ed. Gary Overvold, Philippe Poirier et Lukas Sosoe (Ed.) Paris.

Riley, Patrick (1972) Leibniz. Political Writings, Cambridge University Press, Cambridge.

Rousseau, Jean-Jacques (2013), Projet de paix perpétuelle, Polysynodie de l’Abbé de Saint-Pierre, in Œuvres Complètes, Galimard, Pléiade, Paris, tome III, Paris, 2013, p. 575.

Truyol y Serra (1984) Die Lehre vom grerechten Krieg bei Grotius und bei Leibniz und ihre Bedeutung für die Gegenwart, Studia Leibniziana, XVI/, 60-72.


1 Klassiker des politischen Denkens, Vol I. Von Plato bis Hobbes ; vol II : von Locke bis Weber. Munich, 1976.

2 For a more comprehensive presentation of the basic notions of Leibniz's political thought, see Patrick Riley: Leibniz. Political Writings, Cambridge University Press, Cambridge, 1972, the introduction pp. 1-44; see also Goyard Fabre, La Construction de la paix ou le travail de Sisyphe, Vrin, Paris, 1994, Part I, p. 105-120.

3 “Leibniz stellte die universalische Metaphysik in den Dienst der Politik und entwurf eine Weltrechtsphilosophie (…) Lebniz’ Rechtsmetaphysik spielte in deiser Hinsicht bei der Entwicklung des modernen politischen Universalismus eine Gründerrole” Francis Cheneval, Philosophie in weltbürgerlicher Bedeutung. Über die Entstehung und die philosophischen Grundlagen des supranationalen und kosmopolitischen Denkens der Moderne, Schwabe Verlag, Basel, 2002, p.53. Siehe auch Simone Goyard-Fabre, “L’européanisme des pionniers” in : Regards croisés sur la constitution avortée de l’UE, in: Gary Overvold, Philippe Poirier et Lukas Sosoe (Ed.) Paris, 2011, p. 31- 48.

4 Bertrand Russell, A Critical Exposition of the Philosophy of Leibniz, Allen, London, 1964, p. 202.

5 Patrick Riley, Leibniz. Political Writings, Op.cit., p. 2.

6 Hans Heinz Holz, Sitzungsberichte der Leibniz-Sozietät, 13, 1996, S. 5.

7 Patrick Riley, Op. cit., idem.

8 De Arte Combinatoria, § 42, 190.

9 Opinions on the Principles of Pufendorf in Riley, Patrick, Op.cit. 64- 75.

10 Dialogue entre un habile politique et un ecclésiastique d’une piété inconnue (1679-1682), p. 523.

11 Discours de Métaphysique, (§35, 88) Leibniz speak also of « République générale des Esprits dont le chef est Dieu » (Essais de Théodicée, § 120).

12 Observations on the Abbé Saint-Pierre’s for Perpetual peace (1715).

13 All the references to the Codex Juris gentium are abreviated.

14 Our quotations are taken from Patrick Riley’s translation of the Preface of the Codex Juris Gentium, in Leibniz. Political writings, Op. cit., id. and abbreviated as CJG and quoted in the text.

15 D’Holbach, Le système de la nature, Hildesheim, New York, 1966, Chap. XVI, p. 405.

16 Leibniz, Discours de métaphysique, édition établie, présentées et annotée par Michel Fichant, Gallimard, Folio, 2004, p. 217.

17 Leibniz, Essais de Théodicée, Préface, p. 26-27.

18 Codex Juris gentium, Préface p. 8.

19 Die Werke von Leibniz. Historisch-politische und staatswissenschaftliche Schriften, Hanover (1864-1884), vol V, p. 254.

20 Leibniz, Raison touchant à la guerre ou l’accomodement avec la France (1625) See also A. Truyol y Serra, Die Lehre vom grerechten Krieg bie Grotius und bei Leibniz und ihre Bedeutung für die Gegenwart, Studia Leibniziana, XVI/ 1(1984), 60-72.

21 History will confirm that assertion : after its victories, France saw the creation of coalitions against her ; these eventually isolated the former and shifted the situation (Treaty of Aix-la-Chapelle, Nijmegen and Ryswick).

22 Mémoire de Leibniz à Louis XIV, sur la conquête de l’Egypte, Edit. By M. De Hoffmanns, Edouard Garnot, Paris 1840, p. 3-4. We underline.

23 See J. Zenz Kaplan: Das Naturrecht und die Idee des ewigen Friedens, Brockmeyer 1995, Dortmunder Historische Studien, p. 91-95.

24 Leibniz, Securitas publica, 1670-71, I, 167.

25 Simone Goyard-Fabre, L ‘européanisme des pionniers, in : Gary Overvold, Philippe, Poirier, Lukas K. Sosoe, Op. cit. p. 41.

26 Cf. Entretiens de Philarète et d'Eugène: that text, beyond its circumstance has an ideological dimension.

27 Duhamel, Olivier, Pour l’Europe. Le texte integral de la constitution expliqué et commenté, Seuil, Paris, 2003.

28 Letter to the Abbé de Saint-Pierre » (1715) in: Leibniz. Political Writings, Patrick Riley (Ed.), Op. cit., 176.

29 Op. cit., idem.

30 See Francis Cheneval, Op.cit., p. 112-113.

31 « Everyone knows, Leibniz adds, that Cyneas was the confidante of King Pyrrhus, who advised him to rest, (content with what he has) at once, because that would also have been his goal, as he confesses to him, if he had conquered Sicily, Calabria, Rome an Carthage. » Emeric Crucé’s work particularly deserves mention. He is the author of a work entitled The New Cyneas, Cyneas (1623) being the name of a collection of publications about the project for peace in Europe and around the world. The New Cyneas is full of stories about the Romans, Albanians, Turks and British, about priests, the rich, and thieves, about philosophers, kings and their advisers… It is a diplomatic program intended for monarchs and princes. The preface unveils this program:

“It is necessary before everything else to uproot the most common vice and the one which is the source of all others, namely, inhumanity”.

To do so, Crucé underlines, that what matters first and foremost is to enlighten minds and, secondly, because human society is “one body, of which all the members are in sympathy” with one another, to bring them closer: only then will they reach happiness – the French, Europeans, and lastly, all Christians. For this union, faith in intelligence and reason is necessary and sufficient: not only will it effectively stop the act of resorting to violence, it will smoother the instinct of war itself in humanity

32 Hobbes, Leviathan, chap. XIV, London, Penguin book, 1976, p. 190.

33 Concha Roldán, Pax perpetua y federacion europea. La Critica de Leibniz a Saint-Pierre, in : II” (FFI2010-15914), “Filosofía de la historia y valores en la Europa del siglo XXI” (FFI2008-04279/FISO) y “Enlightenment and Global History” (ENGLOBE: Marie Curie Inicial Training Network: FP7-PEOPLE-2007-1-1-ITN). P. 124.

34 Leibniz, Observations sur le projet de l’Abbé de saint Pierre, Op. cit. p. 181.

35 Jean-Jacques Rousseau, Projet de paix perpétuelle, Polysynodie de l’Abbé de Saint-Pierre, in Œuvres Complètes, Galimard, Pléiade, Paris, tome III, Paris, 2013, p. 575.

36 Letter II to Grimarest: Passages concerning the Abbé de Saint-Pierre’s Project of Perpetual Peace (June 1712). This proposal will be sent to Abbé de Saint-Pierre on the 4th of April 1715 by Leibniz himself.