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Peace, War, and Philosophy


Speculation about war and peace as conditions of interstate relations has tended to divide thinkers into two groupsthose who regard war as inevitable, perhaps even desirable, and those who consider it an evil capable of being replaced by lasting peace through good will or improved social arrangements. The first group is sometimes described as "realist" and the second as "idealist," but these terms have the drawback that such idealist philosophers (in the ontological sense) as Plato and Georg Wilhelm Friedrich Hegel often accept war as a permanent condition of human existence. It is therefore proposed here simply to call the first group "conservatives" and the second "abolitionists," though a wide spectrum of opinion clearly exists within each subdivision.

The Conservative Tradition

the greeks

Ancient Greek thought commonly accepted war between the city-states themselves and between Greeks and "barbarians" as part of the order of nature. The Greek gods were a warlike breed who had come to power after a brutal struggle with the Titans. Ares was one of their leading figures, but the goddess of peace, Irene, was merely a subordinate deity attendant on the great gods. A view of war widely prevalent in Greece was that of Heraclitus of Ephesus. War, Heraclitus taught, was the "father of all and king of all," and it was through war that the present condition of humankind, some men free and some enslaved, had evolved. If strife between the warring elements in nature were abolished, nothing could exist; "all things," according to Heraclitus, "come into being and pass away through strife."

It was not until the later phases of the war between Athens and Sparta (431404 BCE) that a pacifist note unusual in the Greek world was struck in such works as Euripides' The Trojan Women (performed in 415 BCE) and Aristophanes' Lysistrata (411 BCE). Even so, the conclusion drawn by Plato from the Peloponnesian War was that the state must be organized for violent survival in an unruly world. Plato's Republic is, in effect, a design for a military community on the Spartan model. Plato does, however, distinguish between war among Greeks and war between Greeks and outsiders; the former, according to the Republic, is to be legally regulated whereas any excess is permissible in the latter.

christianity and natural law

The conservative acceptance of war as a fact of life was also basic to the intellectual attitudes of the Roman Republic and Empire and was sustained during the Middle Ages, when Catholic writers wrestled with the problem of the conditions on which ecclesiastical approval could be given to the wars of secular monarchs. St. Thomas Aquinas in Summa Theologiae (Question 40), while claiming that peace was the greatest aim toward which man should strive in fulfillment of his natural ends, nevertheless placed on monarchs the duty to defend the state. Similarly, Dante contended in De Monarchia that "peace was the target at which all shafts were sped" but that it was to be attained by the imposition of a world law, if necessary by force, issuing from a revived Roman Empire. The legacy of Christian teaching that had the most lasting influence, however, concerned the application of natural law, strongly tinged by Christian ethics, to the conduct of war.

The Spanish Jesuit theologian Francisco Suárez held that war is not intrinsically evil and that just wars may be waged. Suárez defined three conditions of legitimate war. It must be waged by lawful authoritythat is, by the supreme sovereign; the cause of making war must be just, and other means of achieving justice must be lacking; and war must be conducted and peace imposed with moderation. A similar view was taken by Hugo Grotius, who held that far from war's being a breakdown of the law of nations, it is, in fact, a condition of life to which law is as applicable as it is to the conditions of peace. War, Grotius argued in his De Iure Belli ac Pacis Libri Tres (1625), should not be fought except for the enforcement of rights and, when fought, should be waged only within the bounds of law and good faith. This conception survives in the assumption behind such twentieth-century international organizations as the League of Nations and the United Nations that only wars fought on behalf of international interests, such as the maintenance of world peace, are just.

the advent of nationalism

In the era of European secular nationalism following the Renaissance the idea of war as a necessary or desirable institution strengthened. The Italian city-states of the Renaissance, whose diplomatic practice formed the model for the early European national states, were continually at war with one another; these were, however, limited conflicts that aroused no great indignation among philosophers. A typically acquiescent view of war was that of Sir Thomas More in his Utopia (1518). The Utopians have a pragmatic, not particularly heroic idea of war, which they regard as a normal event; war is to be fought as economically and safely as possible when one's lands are invaded or one's allies are oppressed.

A more profound view was that of the Florentine statesman and writer Niccolò Machiavelli. Like all conservatives, Machiavelli assumed that armed conflict was part of the human lot not because man was evilMachiavelli was inclined to regard man as weak and stupid rather than evilbut because of the activity of malign fate (fortuna ), which is always forcing man to arm himself against adversity. Machiavelli, unlike Heraclitus, held out no hope that war raised man to a higher plane; the prince is condemned to seek victory in war merely in order to survive in the hostile world. In peace a ruler should not sit with hands folded but should always be improving his state's military power against the day of adversity.

At the same time the formation of great national states in England and France was forcing men to speculate on the justification of government, especially since the acceptance of the papacy as the ultimate and sacred authority had been considerably weakened. The concept of a "state of nature" in which men exist without a common superior and in a state of internecine war was introduced to help explain the growth and functions of government. Thomas Hobbes explained in his Leviathan (1651) that war is not the act of fighting but the disposition to fight that exists where there is no common superior to ensure that violence shall not be permitted. Only through the establishment of a commonwealththat is, a superior law-enforcing agency to which all men are subjectcan peace and civilization be ensured. Hobbes did not regard the state of nature as a historical condition that had occurred in the past; he inferred that such would be man's state if the commonwealth did not exist.

John Locke differed from Hobbes in holding that there were natural rights in the state of nature that it was government's function, after its establishment, to protect; hence, war was not a universal condition in the state of nature but occurred only when force was exercised without right. For Locke there was an intrinsic difference between war waged for natural rights and war waged without this sanction. For Hobbes war in the state of nature, as well as war between sovereign states, could be neither right nor wrong since these categories exist only within the commonwealth. Benedict de Spinoza shared Hobbes's view of the inevitability of war where men are without a common government, but, like Locke, he could not reconcile himself to the total absence of morality or law in the state of nature. The Hobbesian argument has nevertheless been of immense importance in shaping modern Western man's attitude toward war and peace. It is that peace is the result of man's determination, deriving from fear of death and the wish for what Hobbes called "commodious living," to create an overriding government. Hobbes did not make clear whether he thought that man could sustain peace in his international relations, but it is clear that, unlike Locke, he considered that nothing short of a world state with a monopoly of power over the nations would suffice to ensure such peace.

Before the Napoleonic Wars, however, war, owing to its limited scale, could not be regarded as the decisive factor in the health or illness of nations. But with the Messianic fervor unleashed by the French Revolution, all Europe appeared to be caught up in revolt against the existing order, internal and external, and the expansion of national wealth showed for the first time the potentialities of nationalistic wars for good or evil. It was in the aftermath of the revolution that the more extreme conservative attitude toward war came into its own in certain countries and war began to be thought of as a positive principle of national regeneration. Germany in particular fostered these views, possibly because that country entered the struggle for national ascendancy somewhat late so that its militarism was proportionately more intense.

Hegel is well known for his conception of history as a struggle of opposites from which a synthesis emerges that transcends the two original conflicting forces. For Hegel the national state was the means by which the Idea realized itself in history. Since the Idea can materialize itself only if the state is allowed to live out its predetermined functions, it follows that the individual's life has no meaning except insofar as it serves the state's ends and that no principle is left by which the relations between states can be subject to moral criteria. Hegel had no patience with the notion of a league of nations for the establishment of permanent peace because he believed war was the catalyst through which history unfolded its purpose. Man must accept war or stagnate.

Arthur Schopenhauer rejected Hegel's idea of the state as the divine expression of justice. For him the state exists because there is injustice; the state is needed to protect man against the effects of his own egotism. In turn, man's egotism and his generally evil nature are a reflection of the dissonances of the Will that for Schopenhauer lies behind the world's realities. Under these conditions war is inevitable, but Schopenhauer, unlike Hegel, did not see war as a progressive factor in history but as a result of the immaturity and weakness of the masses and the love of luxury and power of their strong-willed leaders. Schopenhauer saw no hope of lasting peace.

the militarists

Friedrich Nietzsche may be judged as an extreme representative of the romantic cult of war and as marking the transition to modern totalitarian militarism. Nietzsche was capable of deploring the wastefulness of war; however, in his fully mature writings, Thus Spake Zarathustra (1892) and The Will to Power (first published in 1901), he glorified war and the dangerous life. The phrase "a good war hallows every cause" (Thus Spake Zarathustra ), may be taken as typical of this attitude. For Nietzsche's supermen war is a natural activity, the supreme witness to their superior quality; they should never succumb to the "slave morality" of Christianity, with its accent on humility, submissiveness, and turning the other cheek.

In the teaching of Heinrich von Treitschke the functions of the state were unlimited, as was the individual's duty to submit to its commands. The state's first duty was to maintain its power in its relations with other states and to maintain law within its own borders; its second duty was the conduct of war, the crucible in which the elements in a state's greatness are fused. The hope of a world state or permanent peace is vain; the Aryan race can only keep by the sword what it has won by the sword. Treitschke admitted that the cost of war had risen steeply and, hence, that wars should be shorter and less frequent. But this did not affect the basic axiom that war is the "one remedy for an ailing nation."

Treitschke's ideas were absorbed by the German military writer Friedrich von Bernhardi, who used them to foster the militantly nationalist mood in which Germany entered World War I. In Germany and the Next War, Bernhardi repeated the basic notions of Treitschke: War is the process by which the truly civilized nations express their strength and vitality, life is an unending struggle for survival, war is an instrument in biological evolution. And Bernhardi drew on other conservative writers: Heraclitus; Frederick the Great, whose writings represented war as bringing out man's finest qualities; and Karl von Clausewitz, who described the nation's place in the world as a function of the interplay between its national character and its military tradition.

The conservative-militarist tradition, with its racist overtones, was inherited by the German Nazi and Italian fascist writers of the interwar period, though these added little to the work of their forebears. More recently, the advent of nuclear weapons has made nonsense of the glorification of war, though belief in its inevitability is still not uncommon. Almost the only considerable section of contemporary opinion that believes that national survival after nuclear war is conceivable is that of the Chinese communists. Even they, however, are careful to insist that they would never initiate a nuclear war, and it is, moreover, a feature of all communist thought that the final global victory of communism will remove all cause of war. Communists therefore differ from the conservatives we have considered in that although they regard war as contingent (or perhaps inevitable) in a capitalist system, they have no doubt that permanent peace is attainable under communism.

The Abolitionists

the premodern age

As we have seen, the ancient Greeks (and the same may be said of the writers of the Roman world) were not distinguished for protests against war, though the Stoics of the Roman Empire preached a cosmopolitanism that assumed the oneness of all humankind, making war between its members an affront. When Stoicism was embraced by the Roman emperors, however, it lost its pacifist element, and the same may be said for the early Christian doctrine of nonviolence. Also, during the Middle Ages the fact that the papacy was both the supreme fount of church doctrine and a temporal power of considerable military strength ruled out complete pacifism as a church doctrine.

The outstanding opponent of war during the Renaissance was the great humanist Desiderius Erasmus, though it is incorrect to speak of him as an absolute pacifist. In his Anti-polemus, or the Plea of Reason, Religion and Humanity against War (1510), Erasmus argued that every man's duty was to spare no pains to put an end to war. War was directly opposed to every purpose for which Erasmus conceived man to have been created; man is born not for destruction but for love, friendship, and service to his fellow men.

projects for european peace

During the seventeenth century speculation in Europe about the possibility of permanent peace began to develop, stimulated by growing international commerce and the desire to bind Europe together in a final effort to expel the Turks. This anti-Muslim aim had already figured prominently in the plan for the unification of Europe designed by Pierre Dubois in De Recuperatione Terre Sancte (13051307) and in the celebrated proposal for a federation of Christian princes that George of Poděbrad, king of Bohemia, had presented to his fellow monarchs in 1461. The seventeenth-century proposals were immensely varied, ranging from utterly Utopian ideas to some that might have achieved realization as limited international alliances. Some were limited to Western Europe, others included all Europe, and some embraced the whole Christian world. "The Grand Design" (16201635), probably compiled by the duke of Sully, the chief minister of Henry IV of France, and Some Reasons for an European State (1710) by John Bellers both proposed to divide Europe into provinces of roughly equal size under a common government. A few schemes, such as Emeric Crucé's The New Cyneas, or Discourse of the Occasion and Means to Establish a General Peace and the Liberty of Commerce throughout the World (1623), aimed at the formation of a single world state with all the races and religions under its jurisdiction. In these plans provision was generally made for some form of representative government. William Penn in An Essay towards the Present and Future Peace of Europe (1693) contemplated annual European parliaments; the Abbé de Saint-Pierre in A Project for Settling an Everlasting Peace in Europe (1713) preferred a perpetual congress in order to reflect the viewpoints of the states in his European federation; Crucé called for world assemblies. These confederations were chiefly advocated as defenses of peace, though other aims were also mentioned; Henry IV and the duke of Sully, for instance, had in mind, besides European peace, wars against the Muscovites and Turks and the weakening of the Hapsburgs as the preliminary steps to uniting Europe under French hegemony.

In the eighteenth century these peace plans were given a new lease of life with the French and German Enlightenment. Jean-Jacques Rousseau took the peace project of the Abbé de Saint-Pierre and applied it to the Europe of his own day in A Project of Perpetual Peace (1761), with the insistence that unless the proposed central authority was powerful enough to overawe all the constituent states, the proposal would fail. Rousseau recommended the plan to governments on the ground that a single European authority strong enough to enforce peace would also ensure internal stability in the constituent states. He admitted, however, that governments were probably too shortsighted to appreciate the merits of the plan. A similar project of European confederation was that of Immanuel Kant, titled Eternal Peace (1795). Kant's recipe is notable for its claim that the maintenance of peace requires the achievement of constitutional government by the states.

nineteenth-century peace movements

The nineteenth century was even more prolific in its plans for organizing the nations to ensure peace. In Europe and the United States there arose strong unofficial peace movements that urged the creation of agencies for the arbitration of interstate differences and the equitable settlement of political issues, together with the strengthening and codification of international law. In the atmosphere of harmony that followed the Congress of Vienna the Great Powers of Europe met regularly to deal with threats to peace, while such functional organizations as the European river commissions and the Universal Postal Union (1875) dealt quietly with matters of practical concern to the nations. The hope of a permanent international assembly that might develop into a world legislature was held out at the Hague conferences of 1899 and 1907, and it seemed likely that the growing stake of nations in peaceful intercourse would soon render war obsolete.

The English utilitarians, such as Jeremy Bentham, James Mill, and John Stuart Mill, provided much of the theoretical background of the peace movements. They contended that war was an anachronistic encumbrance on a free society, benefiting no one but aristocrats and professional soldiers. Richard Cobden voiced the commercial classes' distaste for war in his pamphlet Russia (1836). Herbert Spencer, an extreme exponent of laissez-faire society, denounced war in his Social Statics (1851) as an outcome of excessive government authority; with the functions of government reduced and individual liberty restored, all reason for war would disappear. This liberal, economic case for peace culminated in the striking claim by Norman Angell in The Great Illusion (1908) that war had become so destructive of all economic values that nations would never again engage in it.

pacificism and internationalism

World War I disastrously falsified Angell's prophecy; nevertheless, it reinforced the conviction of liberal-minded people that war was an absolute evil and that the creation of expedients to keep the peace, such as the League of Nations and collective security, was the most urgent task of the twentieth century. A strong cleavage now became apparent between absolute pacifistsfor example, H. M. Swanwick, Gerald Heard, Aldous Huxleyand those who supported "just" wars fought under the league's aegisfor example, Gilbert Murray, Lord Cecil of Chelwood, P. J. Noel-Baker. Few of the abolitionists, however, considered a world federation necessary to ensure permanent peace. John Dewey, for instance, argued in the 1920s that it would be sufficient for states to agree to declare war illegal and to prosecute countries that resorted to it as criminals.

The advent of World War II and the invention of nuclear weapons, followed by the failure of the great powers to act unanimously in the United Nations Security Council, raised the question whether the abolitionists' aim can be attained short of the total surrender of national sovereignty. One curious effect of the nuclear stalemate has been to drive many abolitionists into the somewhat conservative belief that peace must be kept by the maintenance of a military balance between the two world camps. Others, like John Strachey in On the Prevention of War (London, 1962), contend that the two superpowers must go beyond this and exercise a kind of condominium over the rest of the world.

The outstanding British philosopher Bertrand Russell continued to believe that the rational conviction of the utter futility of nuclear war can in itself maintain peace provided that the realities of thermonuclear war are widely enough publicized (Common Sense and Nuclear Warfare, London, 1959). As a long-term measure, however, Russell saw no alternative to a world state, which must in the first instance be imposed by one nation or group of nations; only after the world authority has been in power for a century or so will it feel confident enough to base its power on consent rather than force (New Hopes for a Changing World, London, 1951, p. 77). It is not clear, however, whether Russell really wished to pay the price of global despotism in return for peace; elsewhere, he wrote that a new war would be preferable to a universal communist empire (Robert E. Egner and Lester E. Denonn, eds., The Basic Writings of Bertrand Russell, London, 1961, p. 691). Here, in essence, is the issue facing the abolitionist in the nuclear age; whether war is a greater or lesser evil than the imposition on himself and his nation of hostile values which the present anarchic world, with its attendant threat of war, allows him to keep at a distance.

See also Bentham, Jeremy; Dante Alighieri; Dewey, John; Enlightenment; Erasmus, Desiderius; Grotius, Hugo; Hegel, Georg Wilhelm Friedrich; Heraclitus of Ephesus; Hobbes, Thomas; Just War Theory; Kant, Immanuel; Locke, John; Machiavelli, Niccolò; Mill, James; Mill, John Stuart; More, Thomas; Nationalism; Nietzsche, Friedrich; Pacifism; Plato; Renaissance; Rousseau, Jean-Jacques; Russell, Bertrand Arthur William; Schopenhauer, Arthur; Spinoza, Benedict (Baruch) de; Stoicism; Suárez, Francisco; Thomas Aquinas, St.; Violence.


The following are sources for some of the views discussed above.


Bernhardi, Friedrich von. Germany and the Next War. Translated by Allen H. Powles. London: E. Arnold, 1914.

Clausewitz, Karl von. On War. Translated by J. J. Graham. London: K. Paul, Trench, Trubner, 1940.

Guthrie, W. K. C. A History of Greek Philosophy, Vol. I. Cambridge, U.K.: Cambridge University Press, 1962. Ch. 7 contains quotations from Heraclitus.

Hegel, Georg Wilhelm Friedrich. Hegel's Philosophy of Right. Translated by T. M. Knox. Oxford: Clarendon Press, 1942. Especially pp. 209223.

Hobbes, Thomas. Leviathan. Edited by Michael Oakeshott. Oxford: Blackwell, 1960. Especially Ch. 13.

Schopenhauer, Arthur. The World as Will and Idea. Translated by R. B. Haldane and J. Kemp, 3 vols. London, 1909. Especially Vol. III, Ch. 46.

Spinoza, Benedict de. The Political Works. Edited by A. G. Wernham. Oxford: Clarendon Press, 1958. Especially p. 23.

Thomas Aquinas. Selected Political Writings. Edited by A. Passerin d'Entrèves. Oxford: Blackwell, 1959. Especially pp. 159161.

Treitschke, Heinrich von. Politics. Translated by Blanche Dugdale and Torbende Bille, 2 vols. London, 1916. Especially Vol. I, pp. 6170.


Dewey, John. Characters and Events, 2 vols. New York: Holt, 1929. Vol. II, p. 670.

Kant, Immanuel. Eternal Peace. Translated by W. Hastie. Boston, 1944.

Rousseau, Jean-Jacques. A Project of Perpetual Peace. Translated by Edith M. Nuttall. London: R. Cobden-Sanderson, 1927.

secondary sources

Adams, Robert P. The Better Part of Valor: More, Erasmus, Colet and Vives, on Humanism, War, and Peace. Seattle: University of Washington Press, 1962.

Aron, Raymond. Paix et guerre entre les nations. Paris: Calmann-Lévy, 1962. A sociological and historical inquiry into the conditions in international relations that make for war and peace, together with an assessment of proposals for maintaining international equilibrium.

Beales, A. C. F. The History of Peace. London, 1931. A survey of movements, predominantly unofficial, for the promotion of world peace since the creation of the first "peace societies" in 1815. The book includes some useful chapters on nineteenth- and early-twentieth-century ideas on the maintenance of peace.

Hemleben, S. J. Plans for World Peace through Six Centuries. Chicago: University of Chicago Press, 1943. A handy abstract of famous plans for the maintenance of peace since the late Middle Ages.

McDonald, L. C. Western Political Theory in the Modern World. New York, 1962. A useful survey of modern Western political ideas, including thinking on war and peace; the book deals with both secular trends and individual thinkers.

Meinecke, Friedrich. Machiavellism: The Doctrine of Raison d'État and Its Place in Modern History. Translated by Douglas Scott. London, 1957. A translation of Die Idee der Staatsräson in der neueren Geschichte (1924), a treatise on the perennial conflict between the power impulse in human nature and the search for a higher ethical rule in political relations.

Stawell, F. M. The Growth of International Thought. London: Butterworth, 1929. A concise history of pacifism and internationalism.

Vagts, Alfred. A History of Militarism. New York: Norton, 1937. Mainly a study of the ideas and practices of the eighteenth- and nineteenth-century European social movements that sought to make military men the dominant power in the state.

F. S. Northedge (1967)

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