John Locke

Locke imagined people first living without government, equal and free, but inconvenienced by the absence of a settled law and a judge. To remedy that, they agree to form a political society and entrust a government with limited powers for the common good.

The trust runs one way. Government exists for the people, not the people for government, and it holds its authority only so long as it protects their rights. If a ruler turns against the ends of the trust, the people may alter or abolish the government and constitute a new one. Written in defence of the revolution of 1688, the argument was read a century later as a justification for revolution in America and France.

Locke held that certain rights belong to people by nature, before any government exists: the right to preserve one's own life, the liberty to order one's own actions, and the ownership of what one has mixed one's labour with. These are not gifts from the state and cannot be surrendered by entering society.

Government is formed precisely to secure them. That made the rights a standard against which laws could be judged, and it gave later revolutionaries a vocabulary for saying that a government which violates them forfeits its claim to obedience. The phrase 'life, liberty, and property' became, in Jefferson's hands, 'life, liberty, and the pursuit of happiness'.