Despite the apparent prevalence of the victor’s peace throughout history much of the historical record also points to the legitimacy of broader understandings of peace. The idea that peace could be constructed through law, institutions, rights, and prosperity, rather than enforced or merely preserved by military power, emerged slowly during and after the Enlightenment as an advance on the victor’s peace. This was partly in response to violent excesses of elite and state power, and partly to satisfy growing mobilization for a range of rights from within society.
The post-Enlightenment period was the platform for a struggle to achieve a more sophisticated version of peace than any victory in war might allow for. This order was to be more stable than one dependent solely on victory in a conflict, and was gradually seen to be founded upon the creation of both a domestic political and legal architecture and an international architecture designed to balance the interests, needs, and rights of the population. It would have the significant benefit of making the international order more sustainable because it would be based upon a positive peace.
This domestic political architecture may be called the constitutional peace. It has been debated since Plato, Pericles, and Aristotle’s discussions of the ‘good life’, and the merits of democracy versus the role of philosopher kings in ancient Greece.The theme of what shape good government should take emerged again during the Enlightenment in northern Europe. With the Treaty of Westphalia in 1648 it was realized that peace was related to the form the state should take, which should enable it to become a peaceful and accepted member of a stable international order, while also benefiting its population.
As the Enlightenment progressed the Hobbesian view that war was part of the natural fabric of international life, manipulated by Machiavellian princes, was displaced. Leaders, scholars, and general populations began to argue that peace should be central to political life and institutions. Peace was achievable rather than merely an ideal to be aspired to—and this should be thought about in the context of nation-states. Renaissance humanism (which developed during the 14th and 15th centuries AD) emphasized the need for a citizenry, including women, to engage in civic life in the state and follow virtuous courses of action. The liberalism that subsequently emerged challenged the idea that violence and war were part of the natural order of things. Peace could be the product of human ingenuity, especially if states and leaders could be sufficiently engaged. Enlightened actors with liberal views and objectives could now mitigate war.
Another important contribution was the historical argument that ‘just war’ should be waged by a legitimate authority only as a last resort and in response to an act of unjustified aggression. This had two effects: one, a growing concern with the nature of the type of state that would be more conducive to peace, and two, an interest in international organization and institutions designed to create and maintain peace. The constant religious wars of that era in Europe were eventually brought to an end by an agreement along these lines, involving territorial states whose sovereignty might not be violated by other states. The implications were that territorial states and their international arrangements were necessary for a peace built either on common values or on an agreement to differ. Thus, the understanding of peace developed into a balance of power between states, guaranteed through international treaties and alliances, as was endorsed by the Treaty of Westphalia in 1648.
Soon after, John Locke argued that a law-based government would produce consensus, legitimacy, and therefore a domestic peace. A social contract was required in order to cement a consensual and representative relationship between leaders and society, the state providing security and acting as a ‘neutral judge’ to protect the lives, liberty, and property of citizens.
Free trade was an important component of the constitutional peace. Adam Smith’s Wealth of Nations (1776) argued that international trade should be the basis of cooperation, prosperity, and peace between and within states.
Kant, in his book Perpetual Peace, based his subsequent understanding of peace upon the creation of just laws that would be reflected in a ‘republican’ or democratic political order. These conditions would crucially also prevent war between states. Perpetual Peace laid out the conditions through which an early form of social justice could be attained within states and peace could be achieved between states (later to be reflected in the UN Charter in 1945).
Kant’s Perpetual Peace was probably the most comprehensive statement until then of how to bring peace to a Europe that was constantly in turmoil. These arguments gave rise to what has now become known as the liberal democratic peace thesis, for which a huge literature has constructed an argument that supports democratization. Its modern version states that democratic states do not go to war with each other, though they might fight non-democracies. Kant wrote:
[I]f the consent of the citizens is required in order to decide that war should be declared (and in this constitution it cannot but be the case), nothing is more natural than that they would be very cautious in commencing such a poor game, decreeing for themselves all the calamities of war. Among the latter would be: having to fight, having to pay the costs of war from their own resources, having painfully to repair the devastation war leaves behind, and, to fill up the measure of evils, load themselves with a heavy national debt that would embitter peace itself and that can never be liquidated on account of constant wars in the future.
Following these constitutional strands of thinking about peace and order, Jeremy Bentham (1748–1832), a British philosopher and social reformer, added a concern with a number of social issues: welfare, economic freedom, the separation of church and state, freedom of expression, equal rights for women, and the abolition of slavery and the death penalty. He offered the utilitarian insight for government that the greatest happiness for the greatest good would lead to peace, as the British economist David Ricardo (1772–1823) confirmed in an economic sense. Despite the criticism from British economist Thomas Malthus (1766–1834), who believed that surplus populations would lead to unsustainable development, resource depletion, and war, the free trade argument continued to be an essential pillar of the emerging version of peace. However, it was propagated through an uncomfortable mixture of British liberalism and colonialism until the early 20th century.
Liberal thinking was beginning to crystallize into more than speculation: John Stuart Mill (1806–73), a British philosopher, connected development with peace, individual liberty, and private property. He claimed that peace lay in both the protection of individual freedoms and the existence of effective government.
According to the constitutional peace, peace would be constructed through consensual processes so that society would accept its legitimacy. Finding the balance between a Leviathan and the population’s interests has been a difficult task. The problem with Kant’s assumption that states act to maximize the interests of their own peoples (where they treat them as means rather than ends) is that states and elites may exploit their people instead. The line between contributing to peace or following a nationalist or elite interest was, and is, finely drawn.
The emergence of nationalism was also a consequence of what John Stuart Mill identified as the right of people to determine their own government. This may mean pursuing a national interest and identity not necessarily commensurate with regional or international peace or universal norms. As the principle of national self-determination gained popular appeal in the last 100 or so years, especially during the dissolution of the Ottoman and Austro-Hungarian, French, British, and other European empires after World War I and World War II, and at the end of the Cold War (in the Balkans for example), the concepts of both nationalism and ethno-nationalism became associated with the foundations not of order but of war. This soon became a spark for war between groups laying claim to the same territory. It continues to do so in the contemporary era, as the cases of Cyprus, Sudan, Bosnia-Herzegovina, Israel/Palestine, and others suggest.
Another concern has been that the constitutional peace has been characterized as a Christian enterprise, even if it is supposed to be secular. The peace plans had the objective of stabilizing Europe, since the Treaty of Westphalia was essentially based upon Christian ethics and a balance between cosmopolitan and communitarian thought.
Nevertheless, the democratic or liberal peace argument does seem to have held. One of the most significant exceptions has been that democracies may still fight wars against non-democracies, for a range of reasons, as the cases of military intervention in Afghanistan and Iraq in the early 2000s have shown. The democratic peace assumes states will evolve into democracies. Because this has often not been the case, and many states continued to fight wars or infringed their citizens’ human rights, the constitutional peace has proven to be inadequate. It was hoped by Kant and other great thinkers of his era that an international organization aimed at promoting human rights and democracy and keeping the peace would resolve this problem.
The constitutional peace is focused on an elite-level official discourse by state and government, and geographically and temporally bounded by sovereign statehood. All of this is mitigated by its attempt to promote a liberal framework of government for the state, but the constitutional peace project continues to be underpinned by the use of force. However, it remains one of the only ‘laws’ of international relations. Since the end of the Cold War it has been defined by democracy, free trade, and human rights, as Francis Fukuyama notably described in his essay ‘The End of History and the Last Man’ (1989), which celebrated the potential for the spread of democracy after the end of the Cold War.
The liberal-democratic peace thesis is firmly embedded in the current international architecture of peace, in many states’ constitutions, international law, the role of donors, the UN, International Nongovernmental Organizations (INGOs), and International Financial Institutions (IFIs) like the World Bank. As a result, many of the world’s states today have liberal-democratic institutions and constitutions (63% according to Freedom House in 2013), which also involve a commitment to human rights. It is notable that the European Union today owes a great deal of its constitutional structure to the Enlightenment peace projects, which promoted the constitutional peace.
This thinking shaped the frontier of knowledge after the end of the Cold War about what necessary components any state should include in its constitution if it is to remain peaceful. Several states went even further during the last century in their pursuit of peace:according to German Basic Law, Germany is not allowed to have offensive armed forces (a relic of Allied occupation after World War II); Japan (at least until recently) is said likewise to have a ‘peace constitution’, and other countries like Costa Rica have completely dismantled their armed forces.
As a caveat, Kant once remarked that the perpetual peace he envisaged might turn out to be rather unpleasant, and Fukuyama repeated this warning. Liberal democracy and free trade seem to have become the only viable form of politics and peace after the end of the Cold War, but incessant materialism and the related consumption of raw materials might ultimately lead to a hollow victory and even to environmental collapse. In practice the application of the constitutional peace has often been blocked by actors who do not want to share power and who oppose domestic legal structures that might outlaw their authoritarian or corrupt activities. This has not changed since Hitler and Mussolini ignored the League of Nations in the 1920s and 1930s, or when Saddam Hussein ignored the UN over his invasion of Kuwait in the 1990s and blocked inspections of his possible weapons of mass destruction programme in the early 2000s.