20.14.02 · philosophy / political-philosophy

Social contract theory: Hobbes, Locke, and Rousseau on sovereignty and legitimacy

shipped3 tiersLean: none

Anchor (Master): Hobbes Leviathan (1651); Locke Second Treatise (1689); Rousseau Du Contrat Social (1762); Rawls A Theory of Justice (1971); Scanlon What We Owe to Each Other (1998)

Intuition Beginner

Imagine there is no government, no police, no courts. You and everyone else can take only what you can defend. Nobody can make anyone else keep a promise or honour a deal. How would you live? This starting point is what the social-contract writers call the state of nature.

Each thinker first pictures this condition and then asks one question: what agreement would rational people make to escape it? That agreement is the social contract, and its job is to show why government has authority over you. If the rules are ones you would have agreed to, then they bind you; if not, the government lacks a rightful claim to your obedience.

Hobbes, Locke, and Rousseau give three opposed answers. Hobbes says the state of nature is a nightmare of war, so we hand all power to one sovereign. Locke says it is tolerable but insecure, so we set up a limited government to protect our rights. Rousseau says we are corrupted by inequality, so we must rule ourselves together through the general will.

Visual Beginner

A diagram of the three contractarian paths: each begins from the shared state-of-nature node and ends at a different sovereign.

Thinker	State of nature	Reason to contract	Locus of sovereignty
Hobbes (1651)	War of all against all	Fear of violent death	A single absolute sovereign
Locke (1689)	Free but insecure, governed by natural law	To protect life, liberty, property	The people, who may reclaim power
Rousseau (1762)	Peaceful but corrupted by private property	To recover moral freedom	The people as a body, via the general will

The three agree on the device — a founding agreement — and disagree about how much authority it creates and who holds it.

Worked example Beginner

Picture five people sharing one valley with no common authority. Each can grab, hoard, or raid. Even the strongest must sleep, so nobody is safe. If you store food, others have reason to take it; if you plant crops, others have reason to steal them before the harvest. Mutual fear makes a surprise attack the safe option. This is what Hobbes means by a war of all against all ^{[Hobbes 1651]}.

Hobbes says the way out is one move, repeated by each person: "I authorise and give up my right of governing myself to this person, on condition you do the same." Each of the five transfers the right to decide how they live together to a single sovereign. The sovereign is not a party to the deal; the sovereign is the artificial person the five create by authorizing it.

With the transfer complete, the sovereign's commands count as each person's own will. That is why, for Hobbes, the sovereign's power is nearly absolute — rebellion is a person rebelling against a will they themselves authorized. The only limit is that the sovereign must keep the peace, since protection and obedience are reciprocal.

What this tells us: the contract's job is to produce one will where there were five, because one will can keep the peace and five frightened wills cannot.

Check your understanding Beginner

Formal definition Intermediate+

Social contract theory is the family of arguments that ground political authority and legitimacy in a founding agreement — actual or hypothetical — among free and equal persons. Its load-bearing notions ^{[Hobbes 1651]} are:

The state of nature: the condition of persons without a common political authority; for Hobbes a state of war, for Locke a moral order lacking an impartial enforcer, for Rousseau a peaceful pre-social condition undone by property.
The social contract: a hypothetical or historical agreement by which persons institute political society, transferring or pooling rights to constitute a sovereign power.
Sovereignty: supreme authority within a political society — for Hobbes indivisible and absolute, for Locke vested ultimately in the people, for Rousseau inalienable and expressed only through the general will.
Legitimacy: the moral quality that makes coercive rule rightful; on contract theories it tracks whether the arrangement is one the parties could have willed.
Consent: express or tacit agreement; Locke grounds obligation in actual consent, raising the standing problem of whether residence or accepted benefits bind.
The general will (Rousseau): the will aiming at the common good of the people as a body, distinct from the will of all, the sum of private interests.
Authorization (Hobbes): the act by which a person transfers the right to govern himself to a sovereign, so that the sovereign's actions count as his own.
The original position (Rawls): a choice-device in which free and equal parties select principles behind a veil of ignorance, recasting the contract as a procedure for principles.
Contractualism (Scanlon): the thesis that an act is wrong if its governing principle could not be reasonably rejected by others seeking shared principles.

Counterexamples to common slips

The contract is not a historical event. On Hobbes and Rawls the contract is a hypothetical that exhibits the grounds of authority, not a recorded treaty; Hume's empirical objection therefore attacks Locke's historical reading rather than the whole tradition.
Sovereignty is not mere power. A conqueror may possess power without authority; contract theories claim to generate a moral right to rule, the contested element that power alone lacks.
The general will is not majority opinion. A majority can vote against the common interest; Rousseau distinguishes the general will (common good) from the will of all (aggregated interest).
Consent is not sufficient for legitimacy. A contract to enslave is void even if consented to; Locke and Rawls both hold that the content of the contract is constrained by antecedent rights.

Key argument Intermediate+

Argument (the contractarian schema, instantiated across the tradition). The contractarian argument has a fixed skeleton. First, describe the state of nature and show it is untenable. Second, identify the rational exit — the terms persons would agree to. Third, show that the agreement generates authority and obligation. Fourth, fix the resulting locus and scope of sovereignty. Hobbes, Locke, and Rousseau accept the skeleton and diverge at the first step's diagnosis and the fourth step's consequence.

Hobbes's diagnosis is severe. In the absence of a common power, equality of need and vulnerability combined with scarcity makes preemptive attack rational, so the state of nature is a state of war ^{[Hobbes 1651]}. The rational exit is a universal covenant in which each person transfers the right to govern himself to a single sovereign on condition every other does the same. The transfer is mutual and simultaneous, and it generates one artificial person — the Leviathan — whose will counts as the will of every author. Sovereignty is thereby indivisible and absolute, since divided authority reintroduces the war the contract was made to end; rebellion is incoherent, because the rebel denies a will he himself authorized.

Locke's diagnosis is gentler. The state of nature is governed by natural law and is not of itself a state of war, but it lacks a known and impartial judge, settled law, and a common executive, so disagreements escalate into force ^{[Locke 1689]}. Persons contract not to escape humanity but to secure their antecedent natural rights to life, liberty, and property. Government is a fiduciary trust limited by its purpose; because the rights precede the contract, the people retain a right of resistance and of dissolution when the trust is breached. Sovereignty rests ultimately in the community, and the contract generates limited, not absolute, authority.

Rousseau rejects both settlements. The state of nature is not Hobbes's war but a peaceful condition destroyed by the invention of property and the dependence it breeds; the existing contract of the rich is a fraud that legitimizes inequality ^{[Rousseau 1762]}. The legitimate contract is not a transfer to a ruler but an association in which each alienates his rights to the whole community and receives them back as a citizen. Its product is the general will — the common good of the corporate people — which alone is sovereign. Obedience to a law one has helped to make is freedom, and the general will is inalienable and indivisible because it cannot be represented or transferred without being destroyed.

Bridge. This schema builds toward 20.02.01 (theories of justice), where Rawls reuses the contract device not to found a state but to derive principles of distributive justice, and appears again in 20.15.01 (history of philosophy) as the early-modern chapter running from Hobbes through Kant. The foundational reason the contract device recurs is that it converts the question "why must I obey?" into "what could I, as free and equal, have willed?", and this is exactly the move that lets legitimacy be tested against consent rather than asserted by power; the central insight, that authority is the product of an agreement rather than its presupposition, generalises from the founding of the state to the justification of moral principles; putting these together, the bridge is that one and the same device — agreement among free and equal persons — does the work of grounding sovereignty, of limiting it, and, in its modern descendants, of fixing the morality of conduct itself.

Exercises Intermediate+

Exercise 3 (medium, symbolic).

State precisely what each person transfers in Hobbes's covenant and what each retains. Explain why the retained element does not undermine sovereignty.

Hint

The transfer is of the right to govern oneself; the thing retained is what the contract was made to protect.

Answer

Each person transfers the right to govern himself — the liberty to judge and enforce his own preservation as he sees fit — to the sovereign, on condition that every other does the same. What is retained is the inalienable end of self-preservation itself, since the contract's whole point is to secure it. Because the sovereign's will counts as one's own, self-defence against the sovereign is incoherent, so the retained end does not divide authority; it is the purpose for which undivided authority was authorized.

Exercise 5 (medium, symbolic).

Contrast Hobbes's and Locke's accounts of when resistance to the sovereign is permissible. State the structural reason they differ.

Hint

The difference turns on whether rights are transferred away or retained and delegated conditionally.

Answer

For Hobbes, resistance is impermissible in principle because the sovereign's will is the subject's own authorized will, so to resist is to contradict oneself; the only limit is that protection and obedience are reciprocal, so the obligation lapses where there is no protection. For Locke, resistance is permissible because natural rights precede the contract and government is a fiduciary trust: when the trust is breached, the people reclaim the authority they delegated. The structural reason for the difference is that Hobbes transfers the right to govern oneself away, whereas Locke retains it and delegates it conditionally.

Exercise 7 (hard, symbolic).

Reconstruct the step from "the state of nature is a Prisoner's Dilemma" to "rational agents would authorize an enforcing sovereign." Identify the premise that does the work, and one objection to it.

Hint

Track what each agent prefers given the others' choices, and ask what would change those preferences.

Answer

In a Prisoner's-Dilemma state of nature, universal defection (war) is the unique Nash equilibrium and is Pareto-dominated by universal cooperation (peace), so individually rational choice produces a collectively irrational outcome. Rational agents who recognize this would prefer a regime that changes the payoffs so cooperation becomes individually rational — which requires an enforcer who attaches costs to defection. Authorizing such an enforcer is the Hobbesian move. The premise doing the work is that agents can jointly commit to an enforcer whose power outlives each particular choice. The standing objection is that authorization is itself a collective-action problem: the sovereign must be created, and creating it is a further dilemma, so the remedy presupposes the very cooperation it is meant to produce.

Exercise 8 (hard, symbolic).

Rawls calls the original position a contractarian device. State precisely what is contractarian about it and what is not, and distinguish it from Hobbes.

Hint

Contractarian in form; consider what the parties choose, and what motivates them.

Answer

What is contractarian is the structure: principles are justified by showing that free and equal parties would choose them under fair conditions. What is not contractarian, in the Hobbesian sense, is the object and the motivation. The parties choose principles of justice for the basic structure, not a sovereign, and they are moved by the thin theory of the good behind a veil of ignorance rather than by fear of violent death. Unlike Hobbes's bargain among the frightened, the original position is a Kantian construction: the constraints on choice (symmetry, the veil) express the parties' freedom and equality rather than being extracted from them as the price of peace.

Lean formalization Intermediate+

lean_status: none. Social contract theory is a prose-first normative and historical discipline; the correctness gate is argument reconstruction and source fidelity, not formal proof. The part of the subject that admits formal treatment — the state of nature as a strategic interaction, the sovereign as an equilibrium, and social-choice constraints on the general will — is developed in the game-theory and decision-theory chapters (§37, §44), and the modal and deontic logic bearing on rights and obligation is treated in §42. What a human reviewer must verify here is the accuracy of each reconstructed argument and the fairness with which contested positions are presented.

Advanced results Master

The contractarian tradition forks in the twentieth century into two descendants that inherit the device but invert its purpose. The first, Hobbesian contractarianism (Gauthier, Buchanan), keeps the bargain among self-interested agents and asks what constraints rationality alone imposes on their conduct. The second, Kantian constructivism (Rawls, Scanlon), keeps agreement among free and equal persons but drops the premise of mutual self-interest, replacing it with a moral constraint on what counts as a reason. The fork turns on whether the contracting parties are taken as they are — self-interested and frightened — or as morality requires them to be.

Rawls's original position is the pivotal move ^{[Rawls 1971]}. The veil of ignorance strips the parties of their particular ends, so the agreement no longer reflects a bargain among given interests but a choice under conditions that express freedom and equality. The result is Kantian in spirit: the principles chosen are principles that no one could be coerced by others into accepting, because no one knows which person they will turn out to be. The device is contractarian in form — justification proceeds by reference to what would be agreed — yet anti-Hobbesian in content, since the parties do not trade rights for security but select the fair terms of social cooperation.

Scanlon's contractualism generalizes the device from the political to the moral ^{[Scanlon 1998]}. An action is wrong if its governing principle is one that others could reasonably reject as a basis for general agreement; justification is addressed to each person individually rather than aggregated into a sum. The decisive break with Hobbes is the standard of reasonableness: a principle is rejected not because it harms one's interests but because it denies someone the standing that free and equal persons owe one another. Contractualism thus preserves the link between justification and agreement while severing it from self-interest and from the founding of a state.

Hume's "Of the Original Contract" supplies the standing external critique ^{[Hume 1748]}. Hume argues that no historical community was ever formed by explicit consent, that governments originate in conquest and habit, and that obedience is better explained by utility than by promise. The critique is most damaging where the contract is offered as a historical claim (Locke) and weakest where it is hypothetical (Hobbes, Rawls). It forces the tradition to choose between an empirical claim it cannot sustain and a normative claim it must defend on independent grounds — a pressure that did much to reshape the device into the choice-procedure of the twentieth century.

The game-theoretic reconstruction sharpens the Hobbesian core. Read as a symmetric $n$ -person game, the state of nature has a unique equilibrium — universal defection — that is Pareto-dominated by universal cooperation; this is the formal sense in which individually rational choice is collectively self-defeating, and it is the precise premise on which the authorization of an enforcer rests. The reconstruction also exposes the contract's weak point: creating the enforcer is itself a collective-action problem, since each party does better letting others bear the cost of establishing it. The historically influential answers — Hobbes's near-absolute sovereign, Locke's fiduciary trust, Rousseau's general will — are alternative responses to this second-order problem.

Synthesis. Social contract theory supplies the canonical modern analysis of political authority; the argument reconstructed here builds toward 20.02.01 (theories of justice), where Rawls converts the contract from a founding of the state into a procedure for principles, and appears again in 20.15.01 (history of philosophy) as the line from Hobbes and Locke through Rousseau and Kant to the twentieth-century contractualists; the foundational reason the device dominates modern political thought is that it alone makes authority answerable to the consent of those subject to it, and this is exactly why legitimacy, and not mere power, becomes a question at all; the central insight, that the grounds of rule are constructed by agreement among free and equal persons rather than discovered in nature or commanded by force, generalises from sovereignty to morality itself in Scanlon; putting these together, the bridge is that one device — agreement under fair conditions — does the work of founding the state, of limiting it, and of justifying the conduct of persons toward one another.

Full proof set Master

Proposition (the Hobbesian state of nature as a deficient equilibrium). Model the state of nature as a symmetric $n$ -person game in which each player $i$ chooses an action $a_{i} \in {C, D}$ (cooperate, defect) and receives payoff $u_{i} (a_{1}, \dots, a_{n})$ . Suppose the payoffs satisfy the Prisoner's-Dilemma inequalities: for every player $i$ and every profile of the others' actions, $D$ strictly dominates $C$ , that is $u_{i} (D, a_{- i}) > u_{i} (C, a_{- i})$ ; and universal cooperation Pareto-dominates universal defection, that is $u_{i} (C, \dots, C) > u_{i} (D, \dots, D)$ for every $i$ . Then the profile $(D, \dots, D)$ is the unique Nash equilibrium of the game, and it is Pareto-dominated by $(C, \dots, C)$ .

Proof. Fix a player $i$ and an arbitrary profile $a_{- i}$ of the other players. By the dominance assumption, $u_{i} (D, a_{- i}) > u_{i} (C, a_{- i})$ , so $C$ is strictly dominated by $D$ for player $i$ . Since $i$ was chosen arbitrarily, $C$ is strictly dominated for every player, and iterated elimination of strictly dominated strategies removes $C$ for all $n$ players, leaving the single profile $(D, \dots, D)$ . A profile that survives iterated elimination of strictly dominated strategies is a Nash equilibrium, and because it is the only survivor it is unique. By the Pareto-dominance assumption, $u_{i} (C, \dots, C) > u_{i} (D, \dots, D)$ for every $i$ , so this unique equilibrium is Pareto-dominated by the cooperative profile the equilibrium prevents. $□$

This is the formal content of Hobbes's claim that rational conduct in the absence of a common power produces the worst collective outcome. The contractarian remedy is to alter the payoffs so that cooperation becomes individually rational, which is precisely what an enforcer does by attaching costs to defection. The proposition also marks the contract's pressure point: the move from "each prefers an enforcer" to "an enforcer exists" is itself a collective-action problem of the same structure, so the sovereign must be established by some means other than the very rationality the proposition diagnoses as deficient. Locke's fiduciary trust and Rousseau's general will are best read as alternative answers to this second-order problem.

Connections Master

Political philosophy — foundations 20.14.01. This unit specializes the contractarian analysis of authority and legitimacy surveyed there; where the foundational unit treats the questions of justice, authority, and legitimacy together, this unit reconstructs the contract tradition's answer to the authority and legitimacy questions in full historical depth.
Theories of justice 20.02.01. Rawls's original position inherits the contract device and redirects it from the founding of a state to the derivation of principles of distributive justice; the boundary is that this unit treats the contract as an account of sovereignty, while 20.02.01 treats it as an account of the fair distribution of goods.
Democracy 20.07.01. Rousseau's general will — sovereignty inalienable, indivisible, and expressed only by the people — is the direct ancestor of popular-sovereignty and deliberative-democracy theories; the contract tradition supplies the conceptual frame within which democratic authorization is analyzed.
History of philosophy 20.15.01. The line from Hobbes (1651) through Locke and Rousseau to Kant and the twentieth-century contractualists is a continuous chapter of modern philosophy, whose primary texts anchor any deeper historical study of the subject.
Game theory and social choice 37.07.01. The game-theoretic reading of the state of nature as a deficient equilibrium, and the social-choice constraints on a Rousseauean general will (the tension between a single common good and cyclical majority preferences), are developed formally in the game-theory and decision-theory chapters.

Historical & philosophical context Master

Hobbes published Leviathan in 1651 against the backdrop of the English Civil War, arguing that only an undivided sovereign could end the war of all against all; the work's central innovation is the concept of authorization, by which the sovereign is the artificial person constituted by every subject's transferred right ^{[Hobbes 1651]}. Locke's Second Treatise of Government (1689), written to justify the Glorious Revolution, recasts the contract as a limited fiduciary trust for the protection of antecedent natural rights, reserving to the people the right to dissolve a government that betrays its purpose ^{[Locke 1689]}. Rousseau's Du Contrat Social (1762), composed amid the contradictions of absolutist France, denounces existing inequalities as fraud and recasts freedom as obedience to a self-given law, the general will ^{[Rousseau 1762]}.

Kant reframed the contract as a regulative idea: the legitimacy of a state is to be judged as if its arrangement issued from an original contract of free and equal persons — a test rather than an event. Rawls's A Theory of Justice (1971) made the device yield determinate principles of justice through the original position, restating Kantian constructivism in analytic terms ^{[Rawls 1971]}. Scanlon's What We Owe to Each Other (1998) detached the device from the state entirely, using agreement under conditions of mutual reasonableness to ground the wrongness of conduct itself ^{[Scanlon 1998]}. Hume's skeptical "Of the Original Contract" (1748) remains the standing challenge, pressing whether obligation can rest on an agreement that was never actually made.

Bibliography Master

@book{Hobbes1651,
  author = {Hobbes, Thomas},
  title = {Leviathan, or The Matter, Forme, and Power of a Commonwealth Ecclesiasticall and Civill},
  year = {1651},
  publisher = {Andrew Crooke},
}

@book{Locke1689,
  author = {Locke, John},
  title = {Two Treatises of Government},
  year = {1689},
  publisher = {Awnsham Churchill},
}

@book{Rousseau1762,
  author = {Rousseau, Jean-Jacques},
  title = {Du Contrat Social; ou, Principes du Droit Politique},
  year = {1762},
  publisher = {Marc Michel Rey},
}

@book{Hume1748,
  author = {Hume, David},
  title = {Of the Original Contract},
  year = {1748},
  note = {In {\it Essays, Moral, Political, and Literary}},
}

@book{Kant1797,
  author = {Kant, Immanuel},
  title = {Die Metaphysik der Sitten (The Metaphysics of Morals)},
  year = {1797},
  publisher = {Friedrich Nicolovius},
}

@book{Rawls1971,
  author = {Rawls, John},
  title = {A Theory of Justice},
  year = {1971},
  publisher = {Harvard University Press},
}

@book{Scanlon1998,
  author = {Scanlon, T. M.},
  title = {What We Owe to Each Other},
  year = {1998},
  publisher = {Harvard University Press},
}

@book{Gauthier1986,
  author = {Gauthier, David},
  title = {Morals by Agreement},
  year = {1986},
  publisher = {Oxford University Press},
}

@book{Hampton1986,
  author = {Hampton, Jean},
  title = {Hobbes and the Social Contract Tradition},
  year = {1986},
  publisher = {Cambridge University Press},
}

@book{Kymlicka2002,
  author = {Kymlicka, Will},
  title = {Contemporary Political Philosophy: An Introduction},
  year = {2002},
  publisher = {Oxford University Press},
}

@book{HampsherMonk1992,
  author = {Hampsher-Monk, Iain},
  title = {A History of Modern Political Thought},
  year = {1992},
  publisher = {Blackwell},
}

@book{Wolff2006,
  author = {Wolff, Jonathan},
  title = {An Introduction to Political Philosophy},
  year = {2006},
  publisher = {Oxford University Press},
}

Prerequisites

20.14.01

Tier anchors

beginner: Wolff An Introduction to Political Philosophy; Sandel Justice: What's the Right Thing to Do?
intermediate: Kymlicka Contemporary Political Philosophy; Hampsher-Monk A History of Modern Political Thought; Hobbes Leviathan; Locke Second Treatise; Rousseau The Social Contract
master: Hobbes Leviathan (1651); Locke Second Treatise (1689); Rousseau Du Contrat Social (1762); Rawls A Theory of Justice (1971); Scanlon What We Owe to Each Other (1998)

References

Hobbes — Leviathan · 1651, Parts I-II: the state of nature, the laws of nature, authorization, and the sovereign
Locke — Second Treatise of Government · 1689, chapters II-VIII: the state of nature, natural law, property, and consent
Rousseau — Du Contrat Social · 1762, Books I-III: the social compact, sovereignty, and the general will
Rawls — A Theory of Justice · 1971, §3, §40: the original position as a contractarian device and Kantian constructivism
Scanlon — What We Owe to Each Other · 1998, ch. 5: contractualism and principles no one could reasonably reject
Hume — Of the Original Contract · 1748: the empirical critique of the historical contract

Estimated time

beginner: 15m
intermediate: 45m
master: 90m