“On eternal peace” – Immanuel Kant’s contribution to international law

Appreciation on the occasion of his 300th birthday

by Beat Kissling

In 1932, Albert Einstein posed the question in correspondence with Sigmund Freud, from whom he hoped to receive an answer that would provide insight into depth psychology:
  “Is there a way to free people from the doom of war?”
  The cruel experiences of the First World War were still literally ‘in people’s bones’ at the time, while the next barbarism was already in the offing. Freud came to a pessimistic conclusion with his view of the natural human disposition: he supplemented the libido1 in his personality theory with the destrudo2, the death instinct. Other contemporaries drew different conclusions, for example Albert Schweitzer, who interpreted war as a fundamental expression of the “decay of culture”, implying that it is also possible for people to “rebuild culture” in order to prevent wars. Alfred Adler came to a similar conclusion in his 1919 essay “The Other Side: A Mass Psychological Study of a Nation’s Guilt”, pointing out which cultural, political and ultimately psychological elements in social life before and during the war had contributed to the general willingness of most people to march enthusiastically to war. On the one hand, he spoke of the humble veneration of the ruling house, the associated “art of kowtowing”, the gesture of the devote subject3 and thus the fundamental education of the people in “self-insecurity and obedience to superiors”. On the other hand, he considered the dissemination of pure “tall tales” from the General Staff’s kitchen about the inhumanly brutal mentality of the enemy, who could be trusted with any cruelty, as well as the daily, intimidating experience of people being arrested and killed because they had allowed themselves a critical word, to be particularly significant.

People’s longing for (eternal) peace

The war crimes of Hiroshima and Nagasaki are far from people’s minds today, as is the endless suffering during and after both world wars. Most people in Western countries are also unaware that, despite the UN, there have been dozens of wars since both world wars – 90 % of them within countries in Africa, Latin America and Asia – often with an average death toll of around 230,000. In 2022, there were more than 20 wars raging around the world, of which hardly anything was reported in the Western media. It is hard to imagine that the longing for peace and friendship instead of violence and war has not always been present in humanity. We humans are “ultra-social” beings, as the American anthropologist and psychologist Michael Tomasello, among others, was able to illustrate and prove with his research on evolutionary anthropology. However, this does not mean that people are automatically social and peaceful under all circumstances. This depends exclusively on upbringing and socialisation, as Alfred Adler pointed out following the educational ideas of humanism, or what Albert Schweitzer indirectly meant when he spoke of the relevance of the cultural development into which young people grow and to which they orientate themselves. While Albert Einstein, in his correspondence with Freud, emphasises the special role and importance of education when it comes to promoting resilience to the psychosis of hatred in young people, Adler emphasises the helplessness and manipulability of people – he speaks of the “bewitched, enslaved, shamefully abused people” (1919) – as a consequence of the lack of a “unifying bond of mutual trust, a strong, trained sense of community” among people, which is essentially related to upbringing and education.
  The confidence that it would be possible for people to live without war goes back to antiquity and has been expressed as a hope and longing since the beginning of the modern era in the writings of various important humanist-minded personalities, most of whom based their thinking on Christianity. In his main work “The Complaint of Peace”, published in 1517, the great humanist Erasmus of Rotterdam addresses the rulers of his time both inside and outside the church and appeals to them to renounce wealth and domination in the name of the people and religion if war can be avoided as a result. The founder of modern natural law, the Dutch legal scholar Hugo Grotius, contributed a great deal to the revitalisation of the sense of justice in public life in his time with his work “On the Law of War and Peace”, including with regard to the justification of war. Grotius wrote that it was only legitimate to wage war in self-defence, to recover property or for punishment.  Convinced of the fundamental peacefulness of people if they receive a comprehensive, humane education, Jan Amos Comenius (1592-1670), Czech reformer, pioneer of didactics and father of our modern school system, was fundamentally opposed to war despite his own bitter experiences in the Thirty Years’ War (1618–1648). With his pamphlet “The Angel of Peace” (1667) on the occasion of peace negotiations between England and Holland, he tried to convince the parties involved to renounce further war with his peace ethics.
  According to the author of the historical overview work “Calls for Peace and Peace Plans since the Renaissance” from 1953, Kurt von Raumer, the proclaimers of the idea of a possible eternal peace are primarily authors from the 18th century. He writes: “In the 18th century, talk of perpetual peace became one of the most popular themes in European intellectual history”4. The most prominent appearance was the Abbé de Saint-Pierre’s comprehensive work “Projet pour rendre la paix perpétuelle en Europe” 1712/13, which was ultimately made famous by Jean-Jacques Rousseau in particular. According to Raumer, the Abbé succeeded in “popularising the idea of peacemaking”5. In his conception, the idea of a covenant of peace emerges, which “would henceforth decide all disputes through mediation instead of war” and which would also have a “military executive” that could bring any peace-breaker to justice. A court of justice is also envisaged, which is empowered to use “coercive power”, depending on “arbitration and judgement awards”, to ensure that the “protection of the general interest against special interests” is enforced.6 Abbé Saint-Pierre and Rousseau are not the only, but certainly the most prominent representatives of the idea of perpetual peace in the 18th century, which was then taken up by Immanuel Kant and translated by him into a short, very concise treatise, a very far-sighted work with a clear legal or legal-philosophical structure.

The basis of Kant’s idea of peace:
his understanding of human dignity

To mark the 300th anniversary of Immanuel Kant’s birth in 1724, numerous tributes have been published to his comprehensive contribution to the history of ideas and the foundation of an enlightened understanding of the world and man’s relationship to himself and nature. A key text for explaining the idea of the Enlightenment is his essay “What is Enlightenment?” from 1784. The basic programmatic idea is formulated in the very first sentences:
  “Enlightment is man’s emergence from his self-imposed immaturity. Immaturity is the inability to use one’s understanding without guidance from another. This immaturity is  self-imposed when its cause lies not in lack of understanding, but in lack of resolve and courage to use it without guidance from another Sapere Aude! ‘Have courage to use vour own understanding!’ – that is the motto of enlightment.” (Translated by Ted Humphrey, Hackett Publishing, 1992; https://www.nypl.org/sites/default/files/kant_whatisenlightenment.pdf)
  These lines contain the fundamental conviction of man’s general capacity for reason, which everyone can bring to bear, provided that man has dared to use this instrument of independent thought. In the spirit of the Enlightenment, Kant calls on everyone to actively emancipate themselves from the paternalism of the church and other authorities and to trust in their own capacity for reflection and judgement. If someone remains in a state of immaturity, Kant’s diagnosis is bluntly open: this state actually violates the dignity of the person concerned. Only by being self-determined and committed to his conscience – acting as a social being with personal responsibility towards the lives and interests of other people – can he live out his dignity. This view of human nature is reflected in the wording of the first article of the Universal Declaration of Human Rights proclaimed on 10 December 1948:

All human beings are born free and equal in dignity and rights. They are endowed with reason and conscience and should act towards one another in a spirit of brotherhood.

What is special about Kant’s thinking goes beyond the fundamental idea of the Enlightenment, according to which the primary goal of individual emancipation is “happiness”. According to Kant, man strives further, namely for the perfection of his “inner way of thinking” or, in other words, his rational morality. According to Kant, it corresponds to human dignity to act as morally as possible autonomously, i.e., of one’s own free will in accordance with one’s reason. Based on this consideration, he founded the moral formula of the categorical imperative, which allows every human being to ask himself the question of whether he could elevate his actions to a general law when acting according to his capacity for reason.
  Kant turned to the idea of peace as early as 1784 in his essay “Idea for a general history from a cosmopolitan point of view”, when he formulated the goal that this would require a “league of nations [where] even the smallest state could expect security and justice,”. He then took up this idea in 1795 in his draft “On Perpetual Peace”, in which various basic elements of the League of Nations founded in 1920 and the UN Charter of 1945 are already preconceived.

His treatise ‘On Perpetual Peace’

As a formal legal document, Kant’s political treatise contains six preliminaries and three definitive articles. When Kant began to draft this treatise, the states were highly armed against each other. He deliberately did not develop a perfectly developed vision of a world without weapons and war for a distant future, but rather wanted to tackle those aspects in the face of reality that he believed could be realised step by step across states.  The purpose of the preliminary articles is therefore to define points on which agreement can already be reached and which should then serve as preconditions for the definitive treaty. Due to their length, these articles are not explained here verbatim, but summarised in terms of content.
  The first preliminary article insists that peace must be seriously sought by the parties involved; an armistice is not sufficient, especially as experience has shown that this can be used strategically for armament.
  Preliminary Article 2 refers to the fact that a state is not a possession whose elements may be dealt with arbitrarily, as was customary in the form of gifts, marriages, sales, etc. during the feudal era. This source of conflict and violence is thus to be eliminated.
  The third preamble article is intended to gradually prohibit the existence of standing armies (professional armies). “Citizens in arms”, i.e., a militia army for self-defence, is the only form of army permitted under this preliminary law, which is actually the solution known in Switzerland.
  In the following fourth preliminary article, Kant prevents the temptation of states to create risky dependencies through excessive national debt, which harbours a source of armed conflict. On the other hand, he sees no danger in helping each other to improve their civil institutions.
  The two remaining preliminaries are certainly of particular importance and also show Kant’s sound forethought, especially as both provisions contained therein are elements of today’s international law. Article five prohibits the violent interference of a state in the constitution and government of another state. The sixth article could have been taken directly from international humanitarian law, especially as it prohibits the use of methods of warfare that can cause such strong resentment that future opportunities for reconciliation are practically impossible.
  Peace, explains Volker Gerhardt in his excellent interpretation of Kant’s text, is not given to mankind as a gift. It is a “political-legal state that must be established and actively secured. It must, in Kant’s words, be ‘endowed’”.7 In addition to the view that, according to Kant, the political goal of establishing a state is always the foundation of peace, he places particular emphasis on the necessary political activity of individual citizens in order to find the common legal form that allows us to live in secure, peaceful conditions. Everyone must play an active part in this to ensure that discord is not possible on either a small or large scale.
  In contrast to the preparatory preliminary articles, the definitive articles are concerned with specifying the conditions that must ultimately be created in order for peace to be unconditionally valid. The first article reads:

The civil constitution of each state shall be republican.8

Kant starts from the certainty that there can be no secure peace between despotic states. Only if a state’s internal order is guaranteed can its intentions for peace be trusted, Gerhardt explains the underlying idea. Nations that can govern themselves according to liberal legal principles are a prerequisite. According to Kant, freedom is the highest human right and therefore also the most important condition for peace. In the sense of the first definitive article, Kant’s aim is to gradually develop, through persistent reform, a community of citizens who “can speak and act for themselves”.9
  In view of the fact that in Kant’s time there was a lack of practical experience with a functioning republican society – the French Revolution ended in disaster and even in the first republic to prove itself, namely in Switzerland, it took until 1848 for this state to be consolidated – the self-evidence with which he made the development of perpetual peace dependent on the establishment of republican states is enormously far-sighted.
  Kant introduces the following aspects regarding the core of a republican constitution:
  It is a state that guarantees its citizens a life in peace through the “rule of law”. All actions – both private and state – are always bound by this law, which enables legal certainty even beyond national borders. Furthermore, peacekeeping is best guaranteed in a republican state because it is those most affected or suffering from a war – namely the people – who decide on war and peace.
  The second definitive article deals with relations between states. Whereas previous concepts of peace, such as that of Abbé Saint-Pierre, were very concerned with defining and describing the institutional framework conditions of the desired state of peace as concretely and vividly as possible, Kant formulates only minimal preconditions in order to leave the concretisation to practical politics. This second definitive article is correspondingly brief:

The law of nations shall be founded on a federation of free states.10

As with human individuals, the Königsberg philosopher also assumes a lawless state of nature among states in the area of state coexistence and judges the real relationship between the states of his time in exactly the same way, namely characterised by a hostile attitude. Therefore, the external as well as the existing internal peace order between citizens must be secured by law. According to Kant, the same principles should apply in the international peace order as in constitutional law, namely “the principles of freedom and equality, individual autonomy and legal and historical binding force”.11 What is needed is not a superordinate “league of nations”, which would call into question the sovereignty of the individual (free) states, but a system of treaties under international law in the form of legally anchored federalism. Kant already introduced this concept of international law in part of his Preliminary Articles. Preliminary articles 2, 4 and 5, which demand and attempt to guarantee the independence and autonomy of states, have already logically prepared the perspective of federalism.
  The third definitive article follows on directly from this and builds on the idea of state diversity:

The rights of men, as citizens of the world, shall be limited to the conditions of universal hospitality.12

Hospitality means the possibility for every person to travel to all states and to expect to be admitted there as a visitor. As Volker Gehardt writes, this is a “legal policy innovation”, as it grants people positive rights regardless of their nationality. The fact that no right to asylum can be derived from this can be explained by the fact that the first two definitive articles – if they are fulfilled – are not expected to require a right to asylum. In a republic, people decide how they live together, recognising the rule of law. The fact that Kant, in formulating this definitive article, actually deprived the colonial states as such of any legitimisation is explosive. Considering that the end of the colonial era only began to become a reality in the 1960s, it is astonishing how much Kant was ahead of his time.

Kant’s anticipation of
UN principles of international law

The Charter of the United Nations of 1945, as the constitution of the UN and the most important current document of international law, is written in an attitude that expresses the stunned dismay of its authors in the face of the catastrophes of both world wars. It begins with the words:

We the peoples of the United Nations determined to save succeeding generations from the scourge of war, which twice in our lifetime has brought untold sorrow to mankind, […].

And in the first article of the Charter on its purposes and principles, the primary task is exclusively the preservation of peace:

The Purposes of the Unite Nations are: 1. To maintain international peace and security and to this end: to take effective collective measures for the prevention and removal of the threats to the peace […].

The following articles emphasise the need to develop friendly relations with one another, to promote international cooperation – economic, social, cultural and humanitarian – all with a view to respecting human rights and fundamental human freedoms. States should as it continues endeavour to strive for and achieve common goals. The second article of the UN Charter enshrines the principle of equality of all state members and imposes on all the inescapable duty to comply with the provisions of the Charter, which consists above all in never jeopardising peace, refraining from any threats of violence and always refraining from interfering in another state. With slightly different wording or focussing, this approach to international law is in line with that of Kant.
  The UN Charter also includes the Universal Declaration of Human Rights, which, as has already been shown, affirms the dignity and rights of every person and their capacity for reason and conscience as particularly worthy of protection. At the end, it states that they (human beings) should treat each other “in a spirit of brotherhood”, which addresses the central core of international law: human beings all belong to the same species and, despite the diversity of cultures, external differences, etc., are one big family whose members should treat each other as brothers and sisters in a spirit of friendship. In view of his sceptical view of humanity, Kant considers it a compelling necessity on the path to “eternal peace” that the maturity of the individual, his ability to reason in the sense of an enlightened consciousness, must be brought to bear, which requires the recognition and strengthening of the rule of law. However, he trusts people to set out on this path because it is also part of their sense of dignity to want to act with moral integrity.

The connectedness of all people –
 through their common nature

Today – some 230 years after Kant’s writing – we have numerous insights and findings from modern human sciences, as outlined above, which have broadened and deepened our view of the human being. They point in the same direction. A particularly beautiful and impressive way of illustrating the anthropologically coherent perspective of the human family, which would have every reason to feel connected to each other, was the photo exhibition “The Family of Man” by the Luxembourg photographer Edward Steichen after the Second World War. After the war, he had photos of different cultural life sent to him from all over the world. At the beginning of the 1950s, he compiled a comprehensive portrait of humanity from the photos based on 32 essential themes in human life, so that viewers would realise how much the needs and concerns of people all over the world are the same, how similar the lives of individuals are, integrated into different communities, cultural environments and in different phases of life. At the end of the exhibition was a large photograph of an atomic bomb explosion, reminding us of the potential catastrophe that another Hiroshima or Nagasaki would surely mean for the future of humanity.
  The exhibition was first shown in New York in 1955 and later toured the world as a travelling exhibition for several years, helping to strengthen the willingness and desire for peaceful cooperation everywhere. Unfortunately, this emotional, social and intellectual attitude seems to have been largely lost nowadays if you follow current politics, especially in the so-called West. This makes Kant’s impressive treatise of 1795 all the more significant and must be recognised as an extremely valuable legacy which, alongside his other great contributions to the development of intellectual history, can once again be described as a high point of human reflective ability and ethical awareness. His writing has shed a hopeful light of insight into the future of humanity and should definitely be included in the canon of the content of democracy-promoting education in our schools and brought to the attention of young people.  •

1 Libido: the life-sustaining and pleasure-seeking energy in humans
2 Destrudo: the death drive with its urge for death and destruction
3 cf. Heinrich Mann’s novel of the same name Der Untertan (literally “the underling”; English translation of the book: “Man of Straw”, Penguin Books Ltd., 1993); first published 1918
4 Raumer, 1953, p  127
5 ibid., p. 128
6 ibid., p. 13
7 Gerhardt, 2023, p. 74
8 Kant, 1903, p. 120
9 Gerhardt, 2023, p. 84
10 Kant, 1903, p. 128
11 Gerhardt, 2023, p. 93
12 Kant, 1903, p. 137


Adler, A. (1919). The other side. A mass psychological study on the guilt of the people. in: The Collected Clinical Works of Alfred Adler, Vol. 4 – Journal Articles: 1914–1920. Published 2003 by The Classical Adlerian Translation Project, USA
Comenius, J.A. (1993). Angelus Pacis/Angel of Peace. Königshausen & Neumann, Würzburg
Gerhardt, V. (2023). Immanuel Kant’s Draft ‘On Perpetual Peace’. A theory of politics. Wissenschaftliche Buchgesellschaft Darmstadt (2nd, expanded edition)
Institut International de Coopération Intellectuelle (1933). An exchange of letters. Albert Einstein – Sigmund Freud. Printed by imprierie darantiere, Dijon (France)
Kant, I. (1903). On eternal peace. London: George Allen & UNWIN Ltd. Ruskin House, New York, Macmillan
Schweitzer, A. (2007). Philosophy of culture. Decay and reconstruction of culture. Culture and ethics. Published by C. H. Beck, Munich
v. Raumer, K. (1933) Eternal peace. Calls for peace and peace plans since the Renaissance. Karl Alber publishing house, Fribourg/Munic

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