Democratic Peace Theory: Kant’s Heritage and Its Flaws 

Democratic Peace Theory has been an important discussion topic in the International Relations field since the mid-twentieth century, a time when the number of demo-liberal societies rose sharply on the international stage, as a direct consequence of worldwide decolonization processes, eventually becoming the predominant form of government towards the end of the 20th century. In this essay, I will trace back the Kantian origins of this theory to the famous essay Toward Perpetual Peace (1795), which is widely regarded as the philosophical core of the aforementioned theory, since it presented the three tenets that are key aspects of current research projects: republicanism, federations of republics and universal hospitality. I will also address common misunderstandings of Kant’s writings and explore the institutional and normative flaws of the claims proposed by Democratic Peace Theory proponents. Texto de Tomás Correia, PhD Candidate – Philosophy, University of Beira Interior, Department of Communication, Philosophy and Politics. Reviewed by Ricardo Fortunato. Keywords: democratic peace theory, democratic triumphalism, representative democracy, Kant. Cover image: The House of Commons at Westminster, an engraving published as Plate 21 of Microcosm of London, 1808.

1. Introduction

For Immanuel Kant, universal freedom of choice, unrestricted from any constraints and culminating in actions exercised in accordance with pure reason is a value of the upmost importance, one which he tried to extrapolate to the way all societies function. The pursuit of worldwide justice and freedom were put to paper on one of Kant’s most recognizable essays – Toward Perpetual Peace (1795). Kant advances three different mechanisms (embodied in definitive articles) which, he argues, will promote peace between states. The first argument revolves around the condition that every state should have a republican constitution, as a way of creating an accountability mechanism based on the need for “public approval before the government can decide on the use of military force” (Mello, 2016, p.2). The second argument proposes that only a federation of states can overcome an anarchic, and often lawless, international system. The third and last argument consists in guaranteeing universal hospitality for every individual (one of the precursors of what we recognize as “Human Rights” today) and promoting what Kant labelled as “the spirit of commerce” (Kant, 1991, p.10), both of which, cumulatively, will lead to more amicable relations between states.

The Democratic Peace Theory shares many similarities with Kant’s writings and the influence of the Prussian author on the research programs which address the theory is notorious. Modern academics claim that “democracies rarely fight one another because they share common norms of live-and-let-live and domestic institutions that constrain the recourse to war” (Rosato, 2003, p.1). However, this claim has been widely criticized, especially on its normative and institutional frameworks, leading to some discredit in academic circles. Nonetheless, it still maintains its status as an important theoretical explanation for decision-makers in areas of foreign policy, especially in the Western democratic world, spear-headed by the United States of America, where its influence has shaped political action since Wilson’s Presidency in 1912.

Taking into account that the Democratic Peace Theory is intertwined between different fields, namely Political Philosophy, Political Science and International Relations, an adequate study of the theory requires a multi-disciplinary approach. Consequently, in this essay, I will start by clarifying the Kantian basis of the theory’s claims through a deconstruction of the three tenets presented by Kant, while addressing some of its common misinterpretations. I will also question the validity of those claims, present some critiques to the overall concept of the possibility of “democratic peace” and analyze its abusive use by political authorities in order to legitimize democratic “crusades”.

2. On Kant’s Definitive Articles

2.1 Republics and representative democracy

From “A new low for global democracy” in The Economist, February 2022:

Toward Perpetual Peace is commonly regarded as the philosophical precursor of most democratic peace claims (Manan, 2014). The First Definitive Article suggests that one of the fundamental conditions for extended peace is that every state should have a republican constitution based on an adequate representation of the will of the people, separation of powers and respect to the rule of law. Representation is a key feature in Kant’s idealist project of peace. Kant rejects direct democracy in lieu of a representative government; otherwise, since every man would control both the legislative and executive power, such as in the case of the ancient Greek polis, this would mean that “democracy, in the truest sense of the word, is necessarily a despotism, because it establishes an executive power through which all the citizens may make decisions about (and indeed against) the single individual without his consent” (Kant, 1991, p.6). This distinction is of the upmost importance to Democratic Peace Theory proponents, as the constraints on political elites are a huge part of the claims for the absence (or, at least, the drastic reduction) of instances of war between democracies. As Gruyer (2005, p.1) suggests, representative democracies are “governed by citizens who see the security of their property obtaining only under the universal rule of law rather than by proprietary rulers who can always see a neighboring state as a potential addition to their own personal property”.

The fact that representation is an integral part of Kant’s republicanism implies that political elites – the representatives – are in a constant accountability relation towards the citizens they represent, binding themselves to fulfil the volonté générale. Failing to do so has negative consequences for the representatives, since they will be more vulnerable to criticism by the media and the electorate, which will promptly remove them from office and from power positions. Rosato (2003, p.587) provides an explanation on how this mechanism works:

Accountability derives from the fact that political elites want to remain in office, that there are opposition parties ready to capitalize on unpopular policies, and that there are regular opportunities for democratic publics to remove elites who have not acted in their best interests. Moreover, several features of democracies, such as freedom of speech and open political processes, make it fairly easy for voters to rate a government’s performance. In short, monitoring and sanctioning democratic leaders is a relatively straightforward matter.

Rosato (2003, p.587)

This powerful accountability mechanism leads to the main institutional argument for democratic peace. Institutions and political processes in representative republics hold leaders accountable to an enormous range of social groups, lobbies and political adversaries that, more often than not, are opposed to war. War, in theory, only becomes possible if democratic leaders are able to achieve vast popular support for their actions. This is particularly relevant among Western liberal democracies, due to the fact that the dawn of neo-liberalism brought about a heavy international economic interdependence, leading to the sprouting of influential economic groups that oppose to war on terms of the expected costs it poses on investment and international trade. The argument can be summed up in simple terms: domestic groups are often opposed to war because it is usually costly, is deemed morally wrong or there are political gains to be had from opposing groups.

Inherent to accountability, the informational deterrent mechanism also supports democratic peace claims, based on two other factors: transparency and mobilization. Precisely because accountability exists in representative democracies, information must be shared among all citizens. Democratic institutions are usually characterized by their transparency in decision-making processes and reliable signaling to other states in times of crisis. As Mello (2016, p.3) argues: “Democratic institutional procedures foster transparency and they enable a clear communication of political goals. Hence, uncertainty is reduced and misjudgement about a leader’s intentions becomes less likely”. Transparent crisis-solving mechanisms work as a way to counter-act a rising security dilemma. If state A sees a rise in the military capacities of state B, state A will also try to improve its military capacity, leading to yet another response from state B, in an ad aeternum cycle of escalating tensions. The Democratic Peace Theory suggests that this phenomenon is less frequent if both states make their intentions clear. This way, misjudgments regarding other leader’s intentions are less common, leading to a de-escalation of tensions between states.

Other deterrent factor that leads to less war-prone foreign policy is the fact that democracies have very complex military mobilization processes, especially on the early stages of a potential military conflict. In order to prepare a country for war, political leaders usually have to undergo public institutional process, such as requesting authorization from the legislative body. This process is often cumbersome and drags on for months, giving more time for diplomatic (or at least non-violent) resolutions of conflicts. Rosato (2003, p.587) branches this argument in two different mechanisms:

The “slow mobilization” mechanism holds that democracies cannot mobilize quickly because persuading the public and potential anti-war groups to support military action is a long and complex process. The “surprise attack” mechanism shares this insight but also notes that mobilization takes place in the public domain, thereby precluding the possibility of a surprise attack by a democracy.

Therefore, democratic governments are averse to war because they are answerable to their citizens (Doyle, 1986). A state with an executive power that is answerable to a wide variety of social, legal and political institutions, according to a principle of separation of powers and accountability is, in theory, highly constrained and less likely to engage in belligerent activities.

2.2. The Federation of Republics

The second Kantian tenet for peace is the need for a federation of republics which is able to externalize the internal norms of republics. Kant immediately identifies the anarchic nature of the international system, recognizing that states “are a standing offence to one another by the very fact that they are neighbors” (Kant, 1991, p.7). The absence of an international central authority explains why states can only rely on themselves in order to apply the necessary means to ensure their own survival and pursue their own interests. What Kant proposes, in order to solve this issue, is, according to Caranti (2013) an international organization which enables the different competing powers to leave the state of nature that characterizes the international system.

Kant does not, however, make the claim that a federation of republics is a proto-universal state. Contrary to the individual in a state of nature, states are legitimate entities, with autonomy and sovereignty that has to be respected; in Kant’s own words, states “already have a lawful internal constitution, and have thus outgrown the coercive right of others to subject them to a wider legal constitution in accordance with their conception of right” (Kant, 1991, p.7). There is an important caveat which has to be addressed is order to understand this: does Kant refer to a federation composed only by republics or are the entrance criteria less restricted? If Kant’s goal is to achieve worldwide peace, assuming that relations between republics tend to be less warlike and more amicable, then a closed club of republican democracies is no more than a truism. Denying access to well-intentioned states in transitional stages of democratization is a self-debilitating strategy for perpetual peace. Caranti (2013) argues that applying a strict “only-republican” criterion leads to an undermining of the federation itself:

(…) if the relations between two democracies would really need the presence of a joint peace treaty to remain peaceful, then two embarrassing consequences would follow: 1) the normative logic of the theory would collapse (democracies are supposed to respect each other, not to avoid wars between them only if they find them ultimately inconvenient); 2) the role of the federation would be reduced to avoid rare cases in which democracies find war between them useful.

Caranti (2013)

It is not plausible to think that Kant supported a closed club with such a marginal role for the maintenance of peace. What is argued is that the federation should be composed by states that aim to be republican representative democracies, not just the ones that already fill the criteria. This way, diplomatic channels are always open between states, independently of their (formal) republican status, providing more transparency and clearer signaling among them, thus creating conditions for peaceful resolutions of conflicts, international trade and universal hospitality.

2.3 Hospitality, Cosmopolitanism and Commerce

On his third and last tenet for perpetual peace, Kant proposes that one of the essential elements for peace between states is a cosmopolitan right for individuals to visit other states and be received with dignity. A cosmopolitan right arises from the communal ownership of the earth’s surface and becomes “a necessary complement to the unwritten code of political and international right, transforming it into a universal right of humanity” (Kant, 1991, pp.9-10). This universal right acts as a sine qua non for international trade relations and is intrinsically connected to what Kant calls “the spirit of commerce”. What can be extracted from this argument is that by providing a universal right of hospitality to every single individual, Kant tries to secure a prerequisite for extended trade relations (Caranti, 2013).

Caranti further develops his argument by suggesting that Kant introduced a right which has a powerful normative force even without any institution to enforce it, thus laying the foundation of human rights that are considered a compelling tool for peaceful relations intra and inter-state. More than merely establishing a right of visiting or supporting economic interdependence, Kant’s “universal hospitality” should be interpreted as an endorsement of a borderless world, where people are united under a single banner of mutually agreed norms (in this case, human rights), thus guaranteeing a permanent uphold of such norms. As Caranti (2013) concludes:

In this sense, the third article pertains to cosmopolitan right. Through the Third Definitive Article, Kant paves the way of a global community that is best understood as the social side of a supranational entity, of which the federation of peoples and later on the world republic is the institutional coté. On the present reconstruction, then, the third article focuses on the conditions that avoid peoples’ reciprocal closure. It deals with those “good practices” needed to make sure that societies influence one another, know one another, and thus decrease the level of reciprocal diffidence. Mutual knowledge is thus the primary goal of the Third Definitive Article and the exchange of goods is just one of the means through which that end is effectively rendered.

Caranti (2013)

3. Normative Flaws

The normative argument for democratic peace holds that “democracies externalize their domestic norms of conflict resolution when interacting with other states in the international system” (Mello, 2016, p.2). Supporters of this argument assume that states extrapolate their domestic norms when dealing with other states. This democratic ethos, which incorporates norms like dialogue, compromise and peaceful conflict resolution, is expected to exist only when democratic states are interacting with other democratic states (Layne, 1991). However, perception plays an important role on this argument, since it will only be efficient if democratic leaders see other leaders as equally democratic. This leads to two deficiencies in the argument: 1) It only works for inter-democracy relations; 2) It only works if it is well established that both states are stable democracies, not only formally, but also ethically.

If the normative argument were to hold true, the extrapolation of peaceful democratic norms would lead to a lenient conduct on part of democracies in their dealings with other states, democratic or not. However, the argument falls short of its promises. Democratic Peace Theory legitimates pro-democracy intervention in non-democratic states based on the assumption that only democracies can guarantee international peace. Chan (1997, p.59) suggests “this thesis can fuel a spirit of democratic crusade and be used to justify covert or overt interventions against others”. A practical example for this is the United States’ foreign policy since the early 20th century, which has been based on the belief that international promotion of democracy, at any cost, is both useful to promote international peace and enhance United States’ security. This claim has been extensively used by democratic leaders to justify wars of “liberation”, as in the case of President Wilson and the war with Imperial Germany, President Clinton’s intervention in Bosnia Herzegovina and Bush’s invasion of Iraq and Afghanistan (Manan, 2014). Rosato (2003) takes this argument even further, noting that the “interest of state” frequently overrides any respect for democratic norms. The United States’ undermining of left-leaning democracies during the Cold War is enough of a proof to discredit the normative argument. Examples such as the violent overthrow of democratically elected governments in Nicaragua, Guatemala, El Salvador or Chile (at the time already fairly established democracies), in an effort to contain socialist advances, implies that democracies are not reluctant to use violence on other democracies if they see their interests affected.

4. Institutional Flaws

Anti-war protesters in Iran, via NY Times.

The institutional argument suggests “that risk-averse democratic leaders are restrained in their decision-making by a requirement for public support, especially for decisions on war and peace where the human and material consequences can be immense” (Mello, 2016, p.3). Accountability in democratic regimes can be divided in two different factors: public constraints and group constraints. Firstly, the impact of the former can be mitigated by the fact that the burden of war typically falls on a small subset of the population (Rosato, 2003). Almost all modern democracies have professional armed forces, which are publicly financed, that carry out the military needs of the state. In modern warfare, only a fairly limited number of individuals actually partakes in military affairs, as opposed to the conscription mechanism adopted in the earlier 20th century. In the case of a conflict, the professional army deals with the threat and the only tangible costs are the potential loss of a marginal number of citizens and an eventual increase in military expenditures. Secondly, the growth of democracy also brought an increase of citizenship bonds towards the state, which helped minimize the assessment of the costs of war by the general public. Thirdly, democratic political elites have the power to establish narratives that enhance nationalist feelings, since they are perceived as the “voice” of the people, often leading public opinion (instead of following it). Although Democratic Peace Theory portraits most groups in a democracy as anti-war (in coherence with intra-democratic norms), Rosato (2003, p.596) also critiques this view by acknowledging that different groups have varying degrees of influence over decision-makers, arguing that “other more bellicose actors such as the military industrial complex are likely to have just as much at stake and be equally proficient at furthering their own interests”.

Democratic peace theory proponents also claim that information and transparency lead to a clear signaling of intentions; this is not always the case. Rosato (2003, p.598) summarizes the main counter-argument: “democratic processes and institutions often reveal so much information that it is difficult for opposing states to interpret it (…) domestic political competition does not ensure that states will reveal their private information”. This leads to an overload of information, making almost impossible to determine the truly representative signal, with political leaders often using “mental shortcuts” to establish what is expected from the other state. Succinctly, a lot of information is not necessarily good information.


Democratic Peace Theory offers a persuasive and comprehensive approach on international relations that counter-acts the realistic account of the international system (Pugh, 2005). Its Kantian core suggests that perpetual peace can only be obtained through an osmotic process of diffusion of republican principles. It is also important to note that, in order to achieve peace, a federation of states based on republican principles is most effective when it enlarges the scope of admission to all willing states and not just to de facto republics. Additionally, interconnectedness, mutual knowledge and economic interdependence compose an integral part of Kant’s trinity of peace.

The legitimacy of this theory is not just an academic concern, as it is still widely used by political elites in the Western world. Blind acceptance of its claims can lead, as Layne argues (1994, p.46), to potentially dangerous conclusions: “If democracies are peaceful but non-democratic states are “troublemakers” (…) the former will be truly secure only when the latter have been transformed into democracies”. The theory, however, is unable to sustain most of its claims. In its normative logic, it is highly disputable if democracies are actually externalize their domestic norms of trust, dialogue and peaceful resolution of conflicts when interacting with other states. Additionally, more often than not, national interest easily overcomes the internalized democratic ethos of the population and their representatives, which are recurrently able to exacerbate feelings of nationalism. In its institutional logic, accountability rarely works as proposed by democratic peace theorists, as warmongering groups are expected to influence decision-makers as strongly as non-bellicose groups do. Conjointly with the fact that military professionals suffer the largest part of the burden of war and that the costs for the rest of the population is usually not significantly impactful, the accountability mechanisms become discredited (Rosato, 2003). Lastly, information and transparency do little to help political leaders of other states assess the real intentions of democracies, often leading to misconceptions that can be even more prejudicial than having no information at all, as it leads to decisional shortcuts.

In short, democratic peace theory proposes, at best, a convincing, although mostly illusory, peace. As a conceptualization of Kant’s “Definitive Articles for a Perpetual Peace”, modern-day proponents fail to provide convincing arguments to establish that peace can only be maintained by the spread of democracy. More often than not, democracy is a consequence of peace, not a cause (Mello, 2016) and is still widely used as an academic cover for widespread structural violence based of forceful externalization of democratic principles by well-intentioned, but ultimately misguided, democratic leaders.


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