Why should anyone obey a government at all? A common older answer was that kings ruled by divine right. Two English philosophers, Thomas Hobbes and John Locke, answered differently: government is legitimate because free and equal individuals would agree to it. This idea, the social contract, became one of liberalism's foundations.
The state of nature
Both began with a thought experiment: the state of nature. Imagine people living with no government, police or courts. What would life be like, and what would reasonable people agree to in order to escape it?
Hobbes: fear and the sovereign
Thomas Hobbes (1588 to 1679) wrote Leviathan (1651) after living through the English Civil War. His picture of the state of nature is grim. People are roughly equal in strength and cunning, they compete for scarce goods, they fear each other, and no one can be sure of safety. The result is a “war of every man against every man,” in which the life of man is “solitary, poor, nasty, brutish, and short.”
To escape, Hobbes argued, rational people would agree to hand power to a sovereign, one person or an assembly, in exchange for peace. That sovereign must be very strong, because a divided or weak authority would let society slide back into war.
Hobbes was no liberal in his conclusions. He defended near-absolute power and distrusted divided government. Yet he is counted a forerunner of liberalism because of where he started: with equal individuals whose agreement creates authority, for the sake of protecting their lives.
Locke: rights and trust
John Locke (1632 to 1704) published his Second Treatise of Government in 1689, soon after the Glorious Revolution replaced King James II. Locke's state of nature is not a war. It is governed by a law of nature, knowable by reason, which says that since all are equal and independent, no one ought to harm another in their life, health, liberty or possessions. People have natural rights to life, liberty and estate, which Locke grouped together under the word “property.”
How does anyone come to own anything? Locke's answer: by mixing their labor with something not yet owned. Pick apples from a wild tree, or clear and plant unowned land, and you have made it yours, provided you leave “enough, and as good” for others and do not let it spoil.
The trouble with the state of nature, for Locke, is its inconveniences. There is no impartial judge, so everyone judges their own case, and quarrels escalate. So people consent to form a government whose job is to protect their rights more reliably. Government holds power as a trust. If it systematically violates the rights it was created to protect, it breaks that trust, and the people may resist and replace it. This is Locke's right of revolution.
Influence
Locke's ideas echo in the American Declaration of Independence (1776), which says that people are endowed with rights to “life, liberty and the pursuit of happiness” and that governments derive “their just powers from the consent of the governed.”
Objections
Critics raised problems quickly. The Scottish philosopher David Hume, in his essay “Of the Original Contract” (1748), pointed out that most governments were founded on conquest or usurpation, and that few people have ever actually consented to the state they live in. Locke replied in advance with the idea of tacit consent: by living in a country and enjoying its protection, you agree to its laws. Hume answered that a poor peasant who cannot leave has no real choice. Defenders today often treat the contract as a test of legitimacy rather than a historical event.
Worked example: what counts as consent?
Maria was born in a country she never chose. She never signed anything agreeing to its government. Yet she pays taxes, obeys traffic laws and could be jailed for breaking them. Is the government's authority over her legitimate?
A Lockean might answer with tacit consent: by staying, using the roads, accepting police protection and owning property under the country's laws, Maria has implicitly agreed to its authority. If she objected, she could leave.
Hume would push back. Leaving is expensive and difficult. Maria's family, language, job and friends are here. Telling her she consented by staying, Hume suggested, is like telling a man carried aboard a ship while asleep that he agreed to the captain's rule because he did not jump into the ocean.
Modern contract theorists often change the question. Instead of asking whether Maria actually agreed, they ask whether the government's basic rules are ones that free and equal people could reasonably agree to. If the government protects her rights, treats her as an equal, gives her a vote and lets her criticize it, it passes the test even without a signature. If it ruled her by force alone, it would fail, however long she had lived there.
This is how the social contract idea is still used today: not as history, but as a standard for judging whether power is justified.