John Locke

Key ideas

1. No innate ideas. Locke rejects the doctrine that the mind is born with principles stamped on it. The mind begins, in his image, as “white paper, void of all characters”, and every idea comes from experience, through sensation of external things or reflection on the mind’s own operations. The doctrine is often called the tabula rasa, or blank slate.
2. Simple and complex ideas. The mind receives simple ideas passively and combines them into complex ones: modes, substances and relations. Primary qualities such as shape and motion are in bodies, whereas colours and tastes are powers of bodies to produce ideas in us; of substance itself we have only a relative idea, “a supposed I know not what”.
3. Knowledge and probability. Knowledge is “the perception of the connexion of and agreement, or disagreement and repugnancy of any of our ideas”, and it is intuitive, demonstrative or sensitive. Most of what we rely on falls short of it and is a matter of probability, for which testimony and experience are the grounds.
4. Personal identity. A person is “a thinking intelligent being, that has reason and reflection” and can consider itself as itself in different times and places, which it does by consciousness. Sameness of person is therefore sameness of consciousness, not of soul or body.
5. Natural rights and consent. In a state of nature everyone is bound by a law of nature, and has rights to life, liberty and property. Government is created by consent to protect those rights, is held in trust, and may be altered or removed by the people when the trust is broken.
6. Property from labour. Land and goods held in common become a person’s property when that person mixes labour with them, within limits: one may take only as much as can be used before it spoils, and must leave enough and as good for others. Money, which does not spoil, lifts the first limit.
7. Toleration. In the Letter Concerning Toleration, Locke argues that the magistrate’s business is civil interests, life, liberty, health and property, and not the care of souls, because force cannot compel belief. His toleration has limits: he would not tolerate atheists, or churches that give allegiance to a foreign prince.

John Locke (1632–1704) was an English philosopher and physician, one of the first British empiricists and a founder of liberal political thought. His Essay Concerning Human Understanding argues that all our ideas come from experience. His Two Treatises of Government ground political authority in the consent of the governed, and his Letter Concerning Toleration argues that the state has no business coercing belief.

What do we know of his life?

Locke was born on 29 August 1632 at Wrington in Somerset, studied at Westminster School and Christ Church, Oxford, and stayed on as a tutor, taking up medicine under the influence of Robert Boyle. In 1666 he met Lord Ashley, later the Earl of Shaftesbury, and from 1667 served him as physician, secretary and political adviser. After the Rye House Plot of 1683 he fled to Holland, where he completed the Essay, and he returned in 1689 after the Glorious Revolution. The Essay and the anonymous Letter and Two Treatises all appeared in 1689. He spent his last years at Oates in Essex with Sir Francis Masham and Lady Masham, and died on 28 October 1704.

What does the Essay claim?

The Essay attacks innate ideas. Suppose, Locke says, the mind to be “white paper, void of all characters”: where do its ideas come from? He answers that all of them come from experience, through sensation and reflection. Ideas of primary qualities such as shape resemble qualities in bodies; ideas of secondary qualities such as colour do not. Substance, the thing that has the qualities, he can describe only as “a supposed I know not what”. Book III turns to words: our sorts of thing are nominal essences, ideas we form, while the real essences that cause observable properties are unknown.

Knowledge is the perception of agreement or disagreement between ideas, and it is narrow; most of life runs on probability. Testimony is one of its two grounds, and Locke notes that testimony weakens the further it is removed from the original witness. That remark matters most to my own work on what happens to knowledge when people pass on AI answers; the library has the passage.

A person, in Locke’s chapter on identity, is a thinking being that can consider itself as itself in different times and places, by consciousness. If a prince’s soul, carrying the prince’s consciousness, entered a cobbler’s body, he says, the result would be the same person as the prince though not the same man. See personal identity. Two other cases are in the Essay: Molyneux’s question whether a man born blind and made to see could tell a cube from a sphere (Molyneux’s problem), and the possibility that one person’s idea of blue is another’s idea of yellow (the inverted spectrum).

What did he argue in politics?

In the state of nature people are free and equal under a law of nature, with natural rights to life, liberty and property. They enter society by consent so that these may be better protected; government is held in trust, and the people may alter or remove a legislature that betrays it. The library has the Second Treatise.

Property begins when a person mixes labour with what is held in common, limited by spoilage and by the requirement to leave “enough and as good”. Scholars disagree about these limits: C. B. Macpherson read Locke as a defender of unlimited accumulation, while James Tully argued that “enough and as good” still binds once land is scarce.

The Letter says the magistrate’s business is “civil interests”, and “the care of souls is not committed to the civil magistrate”, for the understanding “cannot be compelled to the belief of anything by outward force”. It excludes atheists, whose oaths he thought could not bind them, and churches whose members owe allegiance to a foreign prince. See liberalism.

How does his own record complicate his theory?

Chapter IV of the Second Treatise denies that anyone can consent to be a slave and allows slavery only as “the state of war continued, between a lawful conqueror and a captive”. Yet Article 110 of the Fundamental Constitutions of Carolina (1669), drawn up when Locke was Ashley’s secretary, gave every freeman “absolute power and authority over his negro slaves”. Scholars disagree whether Locke co-authored the Constitutions or mainly drafted them for Ashley. He also held shares in the slave-trading Royal African Company. James Tully and Barbara Arneil add that his account of labour treated land hunted by Native Americans as vacant.

What came after him?

Berkeley argued that abstraction as Locke described it is incoherent, Hume followed him in rejecting innate ideas, and Reid was among his critics. His political writings influenced Rousseau and the American revolutionaries; the Two Treatises are believed to have influenced the Declaration of Independence.

How should you start reading Locke?

Start with Essay II.i (the white paper), II.viii (qualities), II.xxvii (identity) and IV.i (knowledge), and the Second Treatise, chapters II, V, VIII and XIX, with chapter IV for his account of slavery. The Letter is short. All are free.