A change in thinking about warfare can be seen when the writings of Hugo Grotius and Jean-Jacques Rousseau are placed in historical sequence. Grotius wrote during the seventeenth century, when religious conflict, dynastic rivalry, maritime trade, and emerging state power created pressure for rules governing war. Rousseau wrote in the eighteenth century and examined how political association, sovereignty, inequality, and interstate rivalry shaped conflict. The original essay contrasts international unity with national unity and then connects these traditions to Michael Walzer’s account of just and unjust war. That comparison is valuable, but the positions require greater precision. Grotius was not simply a defender of universal peace, and Rousseau was not simply a nationalist who preferred domestic welfare at the expense of international order.
All three thinkers ask whether war can be judged morally rather than treated as a realm where power alone determines right. Grotius develops rules concerning just causes, authority, conduct, property, prisoners, and peace. Rousseau argues that war is a relation between states rather than a natural personal relation among individuals, which creates protections for civilians and defeated soldiers. Walzer revives the just-war tradition in modern form by distinguishing the justice of going to war from justice in the conduct of war. The shift is therefore not a simple movement from international harmony to selfish nationalism. It is a development in how political community, sovereignty, rights, and moral limits are understood.
Grotius and the Historical Setting of War
Hugo Grotius lived from 1583 to 1645 and wrote amid the Dutch struggle against Spanish rule, European religious wars, and expanding maritime commerce. His legal and theological background shaped his effort to identify principles that could govern states even when they disagreed about religion or political interest. His best-known work, On the Law of War and Peace, seeks rules grounded in natural law, custom, treaties, and the practices of nations.
Grotius is often called a founder of modern international law, though international legal thought existed before him. His importance lies partly in organizing a wide range of sources into a systematic account. He assumes that states may resort to war for certain reasons, but he rejects the view that war eliminates all law. Even enemies remain moral agents, and conduct can be judged. (Begby et al., 2012)
Just Causes in Grotius
Grotius identifies defense, recovery of what is due, and punishment of wrongdoing among possible just causes. War should not be initiated merely for glory, conquest, or uncertain fear. The cause must be connected to a violated right. This framework seeks to limit war by requiring justification, but it can also be used expansively when states define their rights broadly.
The original essay says war was considered a last resort during Grotius’s period. Grotius values peace and negotiation, but the modern formal criterion of “last resort” should not be attributed to him without qualification. He supports restraint and examines alternatives, yet seventeenth-century just-war reasoning differed from contemporary international law. His work includes permissions that modern readers may find too broad, especially concerning punishment and colonial encounters. (Grotius, 2005)
Natural Law and International Order
Grotius argues that certain principles bind human beings because of their social and rational nature. States cannot escape all moral obligation simply by asserting sovereignty. Promises, agreements, property, and protection against injury create a framework for international relations. This supports the original essay’s emphasis on international order and economic interaction. Trade and diplomacy depend on trust, navigational rights, and predictable rules.
International peace is not valuable only because it improves economic performance. For Grotius, peace is connected to justice and social order. Commerce may benefit, but legal restraint has moral significance. States should honor treaties and distinguish legitimate claims from opportunistic violence.
Conduct During War
Grotius devotes substantial attention to what parties may do once war begins. He draws distinctions between strict legal permission and moral restraint, sometimes urging moderation beyond what formal law permits. He discusses killing, property destruction, prisoners, surrender, and good faith. This demonstrates that a just cause does not make every method acceptable.
The principle remains central in modern humanitarian law. Even a state defending itself must distinguish military targets from civilians and avoid unnecessary suffering. Grotius’s specific rules are historically dated, but his insistence that conduct remains accountable helps establish the intellectual background of jus in bello.
Rousseau’s Political Context
Jean-Jacques Rousseau wrote in the eighteenth century, before the French Revolution but during a period of debate about monarchy, republics, inequality, and popular sovereignty. His political thought asks how people can obey law without surrendering freedom. The social contract creates a political community governed by the general will, at least in the ideal theory. (Rousseau, 1997)
The original essay connects Rousseau with citizen rights and national priorities. Rousseau does emphasize the political community, but he is deeply critical of interstate competition and the war-producing character of the European state system. He does not celebrate war as an expression of national self-interest. His writings often portray modern states as insecure, mutually suspicious, and driven toward conflict.
War as a Relation Between States
One of Rousseau’s most influential claims is that war is not a relation between one person and another but between states. Individuals become enemies only accidentally as soldiers, not as private persons or citizens. Once a soldier lays down arms and surrenders, that person ceases to be an enemy and should not be killed. This principle limits violence against civilians and defeated combatants.
This argument challenges the idea that enemy populations may be treated collectively as criminal or subhuman. The state may be the object of conflict, but ordinary people retain moral status. Rousseau’s position therefore strengthens humanitarian restraint rather than making warfare more subjective according to national desire.
The General Will and National Political Unity
Rousseau’s theory of the general will gives the political community a strong moral role. Citizens should participate in making laws directed toward the common good rather than obeying private rulers. This can be interpreted as national unity, but it is not simple majority domination. The general will is not whatever the numerical majority happens to want; it is the shared interest of citizens considered as equals.
The theory nevertheless creates risks. Leaders may claim to represent the general will and suppress dissent. Later nationalist movements sometimes used ideas of popular sovereignty for purposes Rousseau did not specify. His work should therefore be distinguished from every political use made in his name.
Rousseau on International Federation
Rousseau considered proposals for European peace and recognized the potential value of federation. At the same time, he doubted that sovereign rulers would surrender enough power to make a federation effective. The interstate system creates incentives for expansion and insecurity. Domestic political legitimacy alone does not guarantee peaceful foreign policy.
This complicates the original contrast between international peace under Grotius and national peace under Rousseau. Rousseau understands the need for international order but is more pessimistic about achieving it through voluntary agreement among existing states. His analysis anticipates later theories of the security dilemma and institutional weakness.
Conservatism and Progressiveness
The original essay labels Grotius conservative and Rousseau progressive, then links these terms with communism and capitalism. These associations are not historically accurate. Grotius defended natural law and legal order but also supported commercial freedom and aspects of Dutch expansion. Rousseau criticized inequality, luxury, and modern commerce but was not a communist in the later economic sense. The categories conservative and progressive can be used only with careful definition.
A more useful contrast concerns legal continuity and political foundation. Grotius works largely within a world of states, rulers, property, and inherited legal traditions, seeking to regulate them. Rousseau asks how legitimate political authority can arise from free and equal citizens. Grotius systematizes rules across political communities; Rousseau questions the moral basis of the communities themselves.
Michael Walzer and the Revival of Just-War Theory
Michael Walzer’s Just and Unjust Wars analyzes war through moral language embedded in law, history, and public argument. He rejects both absolute pacifism and realism that treats morality as irrelevant once states fight. Walzer distinguishes jus ad bellum, the justice of entering war, from jus in bello, justice in how war is conducted. A state may fight for a just cause and still commit war crimes; soldiers fighting for an unjust state may still be obligated to obey rules protecting civilians. (Walzer, 2015)
This distinction relates to Grotius’s effort to separate causes and conduct. Walzer develops the argument in response to modern state warfare, total war, guerrilla conflict, terrorism, and humanitarian intervention. His work is not simply conservative or progressive in party-political terms. It defends moral limits that can criticize any belligerent.
Aggression and the Legalist Paradigm
Walzer treats aggression as the central crime of war because it violates the territorial integrity and political sovereignty of a community. The victim state has a right of defense, and other states may assist it. This “legalist paradigm” resembles domestic law in which individuals possess rights against attack. The analogy is imperfect because states are not persons, but it establishes a presumption against force.
Rousseau’s state-centered definition of war helps explain why political communities, rather than private individuals, are the primary parties. Grotius’s natural-law framework supplies earlier reasoning about violated rights and defense. Walzer translates these traditions into a modern moral vocabulary.
Noncombatant Immunity
Walzer argues that civilians should not be targeted because they are not engaged in the dangerous activity of war. Combatants become liable to attack because of their role, while civilians retain immunity. This principle resonates strongly with Rousseau’s claim that individuals are enemies only as soldiers. It also continues Grotius’s concern with limits, although Grotius’s historical permissions were sometimes broader than modern standards.
Noncombatant immunity does not mean civilians are never harmed. Military action can create foreseeable incidental harm, which raises questions of proportionality and precautions. Modern humanitarian law requires distinction and prohibits attacks expected to cause civilian harm excessive in relation to the anticipated military advantage.
Proportionality
Proportionality operates at more than one level. In deciding whether to go to war, expected goods must be proportionate to the harms. During war, the harm expected from an individual attack must not be excessive relative to the concrete military advantage anticipated. The original essay’s contrast between universal welfare and majority power does not capture this structure.
Proportionality is difficult because values cannot be calculated with certainty. Decision-makers must use available evidence, distinguish military objectives, and consider alternatives. The concept is not permission to balance away every right; direct attacks on civilians remain prohibited regardless of expected advantage.
Supreme Emergency
One of Walzer’s most debated arguments concerns “supreme emergency,” a situation in which a political community faces an imminent and morally catastrophic threat. He suggests that extraordinary measures may become defensible under extreme conditions, though he treats this as a tragic exception rather than ordinary policy. Critics argue that such exceptions weaken civilian immunity and can be invoked too easily by states.
This debate illustrates tension between rule and survival. Grotius, Rousseau, and Walzer all recognize political necessity, but moral theory attempts to prevent necessity from becoming a blanket excuse. Emergency claims require rigorous scrutiny because every belligerent is tempted to describe its own cause as exceptional.
Conservative and Progressive Political Parties
The original essay attempts to relate Grotius and Rousseau to conservative and progressive parties, stating that conservatives protect the welfare of all while progressives allow the powerful majority to dominate. This account is too simplistic and reverses several common associations. Modern conservative and progressive traditions contain varied positions on war, sovereignty, human rights, intervention, and military spending. Neither side possesses a monopoly on concern for minorities or public welfare.
The historical thinkers are more useful as sources of questions than as labels for current parties. Grotius asks what legal and moral rules bind states. Rousseau asks what makes political authority legitimate and why the state system generates conflict. Walzer asks how communities may defend themselves without abandoning moral limits. Current policies can be evaluated through these questions without forcing the philosophers into contemporary partisan categories.
International Law Today
Modern international law generally prohibits the threat or use of force except in self-defense, with authorization from the United Nations Security Council, or under debated and limited doctrines. International humanitarian law regulates conduct through the Geneva Conventions, customary law, and related treaties. These rules reflect centuries of argument rather than the work of one philosopher. (United Nations, 1945)
Grotius contributed to the tradition of international legal obligation, Rousseau clarified the status of civilians and soldiers, and Walzer explains the moral language through which legal rules are often defended or criticized. Law and morality overlap but are not identical. An act may be legally uncertain yet morally condemnable, or legally permitted yet ethically troubling.
War, Economy, and Political Community
The original essay connects Grotius’s international order with economic performance. Peace supports trade and development, while war destroys infrastructure, displaces people, interrupts education, and redirects resources. Yet economic interest can also generate conflict over territory, resources, and commercial access. International law attempts to make competition less violent, but it cannot eliminate political ambition.
Rousseau warns that societies organized around comparison, luxury, and inequality can become restless and competitive. Walzer emphasizes that economic advantage does not create a just cause. A state cannot lawfully or morally invade merely to improve prosperity.
Minorities, Majorities, and the Common Good
The original essay expresses concern that powerful majorities may impose their will on minorities. This concern is relevant to both domestic and international ethics. Rousseau’s general will should protect common freedom, but institutional safeguards are needed to prevent majority domination. Grotius’s universal law requires rules that do not depend solely on power. Walzer’s rights-based approach protects individuals from being sacrificed casually for collective goals.
A just political community must combine democratic authority with rights, accountability, and minority protection. A just international order must similarly prevent powerful states from defining law according to their advantage. Moral equality is the principle linking the levels.
Conclusion
The development from Grotius through Rousseau to Walzer shows changing ways of thinking about war, sovereignty, and moral restraint. Grotius systematizes natural-law and international rules governing just causes and conduct. Rousseau locates legitimate political authority in free citizens and argues that war is a relation among states, protecting civilians and surrendered soldiers from treatment as personal enemies. Walzer adapts the just-war tradition to modern conflicts through distinctions between aggression, defense, combatant liability, civilian immunity, and proportionality.
The original essay correctly identifies a shift in warfare thought and a relationship with Walzer, but the shift should not be described as simple movement from international unity to selfish national unity or from conservatism to progressiveness. Grotius, Rousseau, and Walzer each value political community while also placing limits on its use of force. Their shared contribution is the rejection of the idea that war suspends morality. Even under conditions of danger, states, leaders, and soldiers remain answerable for why they fight and how they treat human beings.
Bibliography
Begby, E., Reichberg, G. M., & Syse, H. (2012). The ethics of war. Part I: Historical trends. Philosophy Compass, 7(5), 316–327.
Grotius, H. (2005). The rights of war and peace (R. Tuck, Ed.). Liberty Fund. (Original work published 1625)
Rousseau, J.-J. (1997). The social contract and other later political writings (V. Gourevitch, Ed. & Trans.). Cambridge University Press.
Walzer, M. (2015). Just and unjust wars (5th ed.). Basic Books.
United Nations. (1945). Charter of the United Nations.
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