The book follows him from a boyhood in the English Civil War, through medical practice and the household of Lord Ashley, later the Earl of Shaftesbury, to exile in Holland and the months after the revolution of 1688, when his major works reached the public.
It explains the Essay Concerning Human Understanding: the case that the mind begins without innate ideas (the idea popularly called the blank slate), the accounts of substance, language and personal identity, and the rule that belief should be proportioned to evidence. It covers the Two Treatises of Government, from the attack on the divine right of kings to the theory of property, government as a trust resting on consent, and the right of resistance. It also treats the Letter Concerning Toleration and its limits, the writings on education, Locke's work for the Carolina proprietors, and the disputed place of slavery and Indigenous land in his thought.
The closing chapters follow the long argument over his legacy, from Voltaire and the American Revolution to Strauss, Macpherson, Dunn and Rawls. Where scholars disagree, as they do about his theory of property and his religious aims, the disagreement is set out.
The book assumes no background in philosophy. Terms are explained where they first appear, and it ends with a timeline and an annotated guide to Locke's own works and the main scholarship on them.