In 1689 a man in his late fifties came home from exile and published, in a single rush, the two books that founded the modern world's way of thinking about the mind and the modern world's way of thinking about the state. The Essay Concerning Human Understanding argued that the human mind arrives empty and is furnished entirely by experience. The Two Treatises of Government argued that no king rules by God's gift, that legitimate power rests on the consent of the governed, and that a government which turns predator may be dissolved by the people who set it up. A Letter Concerning Toleration came the same year, drawing a wall between the magistrate's sword and the individual conscience. Three books, one year, and most of the next three centuries was downstream of them.
He put his name on only one of them. The Essay went out as Locke's; the Two Treatises and the Letter went out anonymously, and Locke denied authorship of the Treatises for the rest of his life, acknowledging the book only in a codicil to his will, after he was past being prosecuted for it. This was not vanity and it was not modesty. He had just spent six years hiding in the Dutch Republic under assumed names because the English government suspected him, correctly, of association with men who plotted against the crown. A book arguing that subjects may overthrow a tyrant was not a thing a careful man signed.
Careful is the word for the whole life. John Locke was born in a Somerset village in 1632, the son of a country lawyer who had ridden as a captain for Parliament in the civil wars. He was schooled at Westminster while a king was being tried and beheaded a few hundred yards away, went up to Oxford, trained in medicine, and might have passed into history as a competent physician had he not, in 1666, fallen into the orbit of one of the most powerful and dangerous politicians in England.
That politician, Anthony Ashley Cooper, soon the Earl of Shaftesbury, nearly died of a liver cyst, and Locke ran the operation that drained it, inserting a silver tube that stayed in the wound for the rest of the earl's life. The earl decided this physician was the cleverest man he had ever met and pulled him into the center of English politics, where Locke wrote on trade, on toleration, on the colony of Carolina, and absorbed, at close range, a brutal education in how power actually works and how it actually falls. When Shaftesbury's faction lost and fled, Locke fled with it.
So the man who wrote that the mind is white paper and that government is a trust was no cloistered scholar. He was a physician, a colonial administrator, a political operator, and for six years a hunted exile, and he built his philosophy out of a hard-won conviction that runs through both books at once: do not take a thing on authority, whether it is an innate idea the mind is supposedly born with or a divine right a king is supposedly born with. Check it against experience. Ask what it actually rests on. And where it rests on nothing, say so.
The break
Two settled assumptions stood in Locke's way, one about the mind and one about the state, and the striking thing is that he broke both with the same instinct in the same year. The first assumption was that the mind comes furnished. The dominant view, running from Plato through Descartes, held that some of what we know is innate, stamped on the mind before any experience: the basic truths of , the idea of God, the first principles of morality, knowledge the mind possesses simply by being a mind. The second assumption was that political authority comes down from above. The reigning theory of Locke's England, argued most fully by Sir Robert Filmer, held that kings rule by divine right, their authority descended in an unbroken line from the fatherly power God gave Adam over his children; subjects owe obedience the way a child owes a parent, not by any choice of their own.
Both assumptions deserve their due, because both are the natural ones and both held the field for centuries. That some knowledge is built in feels obvious: a child seems to grasp that a thing cannot both be and not be without ever being taught it, and surely the mind must bring something of its own to experience or it could make nothing of it. And that authority descends from above had the weight of the whole order behind it: a settled hierarchy with God at the top and the king beneath him, each rank receiving its due from the rank above, was how Europe had understood legitimacy for a thousand years. Neither assumption was stupid. Each was the considered position of serious people.
Locke's break is to run the same demand at both. Against innate ideas he asks for the experiential receipt: if a principle were really stamped on every mind at birth, every mind would assent to it, and yet children, the uneducated, and whole peoples assent to no such universal principles, not even the idea of God, so the innate furniture is a fiction and the mind must start empty. Against divine right he asks for the receipt too: where, exactly, is the unbroken descent of Adam's fatherly power, and how would anyone trace it to a living king, and why would fatherhood confer political rule at all? It cannot be shown, so kingship by inheritance from Adam is a fiction, and legitimate power must come from somewhere a person can actually point to: the consent of the people who live under it.
The single move under both books is the refusal to accept a thing as given just because it has always been handed down as given. The mind is not pre-furnished with truths it never learned; it is white paper, and experience does the writing. The state is not pre-furnished with a ruler it never chose; it is built by agreement, and consent does the authorizing. Knowledge is constructed from the ground up out of what the senses supply, and authority is constructed from the ground up out of what free people agree to, and in both cases the structure can be no more legitimate than the foundation it actually stands on. That is one instinct, applied to the mind and to the state in the same remarkable year, and it founded empiricism and together.
Chapter 1
The physician who ran the revolution from the library
"The labour of his body, and the work of his hands, we may say, are properly his."
He was born on 29 August 1632, in the village of Wrington in Somerset, in the west of England, into a Puritan family of modest standing. His father, also named John Locke, was a country attorney and small landowner who served as a captain of horse on the Parliamentary side when England fell into civil war, the long struggle between King Charles I and Parliament that ended with the king's execution in 1649. Locke was sixteen and a schoolboy at Westminster, in London, when that execution happened, close enough to the event to feel its weight; a country could kill its king, and the question of where authority legitimately comes from was not abstract to anyone who lived through it.
From Westminster he went up to Christ Church, Oxford, in 1652. He found the official curriculum, still heavily medieval and Aristotelian, tedious, and gravitated instead toward the new experimental science and toward medicine. He worked alongside the physician Thomas Sydenham and trained to practice medicine, absorbing from it a habit of mind that never left him: observe the particular case, distrust grand systems spun out of first principles, and accept that much of what one would like to know simply cannot be known. That clinical modesty about the reach of knowledge becomes, decades later, the spine of his philosophy.
The turn of his life came in 1666, when he met Anthony Ashley Cooper, soon to be the first Earl of Shaftesbury, one of the most powerful and most dangerous politicians of the age. Two years later Cooper developed a cyst on his liver that threatened to kill him, and Locke directed the operation to drain it, inserting a silver tube through which the wound could be cleaned, a tube that reportedly stayed in place for the rest of Cooper's life. The earl, convinced Locke had saved him, made the physician his secretary, adviser, and confidant, and brought him into the machinery of English politics. Locke wrote memoranda on trade and on currency, took a hand in the affairs of the American colony of Carolina, and watched, from inside the room, how power is won and lost.
Shaftesbury became the leader of the faction that tried to bar the king's Catholic brother James from the throne, and when that effort collapsed and Shaftesbury fell, suspicion fell on the men around him. After the Rye House Plot of 1683, an alleged conspiracy to assassinate the king, Locke, by then deep in writing the Two Treatises, judged it prudent to leave the country. He fled to the Dutch Republic in September 1683 and spent nearly six years there, partly under assumed names, while the English government watched for him. Exile was not a retreat from the argument; it was the argument's price.
Then the politics turned. In 1688 the Glorious Revolution drove James from the throne and brought in William of Orange and his wife Mary, James's Protestant daughter, on terms set by Parliament, a near-bloodless demonstration that a people could change its rulers. Locke came home in February 1689, sailing in the convoy that carried Mary across the North Sea. Within the year he published the three books he had been building for two decades, the Essay, the Two Treatises, and the Letter Concerning Toleration, and only one of them under his own name. He never married. He spent his last years at Oates, the Essex country house of his close friend Lady Damaris Masham, herself a philosopher, and he died there on 28 October 1704 while she read the Psalms aloud to him, having furnished the modern world with a theory of how a mind learns and a theory of when a government may be unmade.
Chapter 2
White paper: the mind starts empty
"Let us then suppose the mind to be, as we say, white paper, void of all characters, without any ideas. How comes it to be furnished? ... To this I answer, in one word, from experience."
The Essay Concerning Human Understanding opens by clearing away a rival, and the rival is the most respectable position in philosophy. It is the doctrine of innate ideas: the view, descending from Plato and held in Locke's own century by Descartes, that the mind is born already stocked with certain truths it never had to learn. The candidates were the prestigious ones: the basic laws of logic (a thing cannot both be and not be), the idea of God, the first principles of right and wrong. On this view the mind brings real knowledge to experience, knowledge stamped in before the senses ever report anything.
Locke spends the whole first book of the Essay dismantling this, and his central argument is disarmingly simple. The usual proof of innateness was universal consent: everyone agrees to these principles, so they must be built in. Locke turns that proof against itself. If a principle were truly innate, present in every mind from birth, then every mind would in fact assent to it, including the minds of small children and those incapable of abstract thought. But children do not assent to the law of non-contradiction; they have never heard of it and could make nothing of it if they had. Whole peoples, Locke notes, have lived without the idea of God, which was supposed to be the most securely innate idea of all. Universal consent does not actually hold, and even where most people do come to agree on something, that is easily explained by their all learning it the ordinary way, through experience, which makes the innate hypothesis an extra wheel that turns nothing. Strike it out.
Which leaves the mind empty, and gives the Essay its founding image. The mind at birth, Locke writes, is to be supposed "white paper, void of all characters, without any ideas," and the whole question of the book is, "How comes it to be furnished?" His answer is the single word on which all of empiricism rests: "in one word, from experience." There is no innate furniture. Every idea the mind will ever hold gets written onto the blank page by experience and by nothing else. (The famous Latin tag for this, tabula rasa, the scraped tablet, is not Locke's phrase; it appears nowhere in the Essay. It is an older label, running back through Aquinas to Aristotle, that later writers pinned onto Locke. He wrote about white paper.)
Experience writes through two doors, and naming them precisely is the heart of the system. The first is sensation: the five senses reporting the outer world, delivering the ideas of color, sound, heat, hardness, shape. "This great source of most of the ideas we have," Locke writes, "depending wholly upon our senses... I call sensation." The second door is subtler and is Locke's own addition, the thing that lets him claim experience can account for everything in the mind and not just reports of the outside. It is reflection: the mind turning around to observe its own operations, noticing itself perceiving, doubting, believing, willing, remembering. "The ideas it affords," he writes, are "such only as the mind gets by reflecting on its own operations within itself." Watching a sunset is sensation; noticing the watching, and forming from that the idea of perception itself, is reflection. The outer sense reports the world; the inner sense reports the mind. Between the two doors, nothing else is needed.
Everything the mind contains is then built out of what comes through those doors. The atoms of the system are simple ideas, the ones experience delivers whole and the mind cannot make for itself: the particular red of a thing, the warmth of it, the sound it makes. A simple idea cannot be conjured; it has to be supplied. A man born blind has no idea of scarlet, because no door ever let one in, and no effort of thought can manufacture it. What the mind can do is work on the simples it has been given, combining, comparing, abstracting. It glues simple ideas into complex ones (it has seen gold and seen mountains, so it can build a golden mountain it has never seen); it sets ideas side by side to see how they relate; it strips the particular away to form a general idea, taking the many men it has met and abstracting the idea of man. The whole furniture of an adult mind, however elaborate, is assembled this way, out of parts that all entered as experience. Nothing comes from nowhere, and that single rule is the one the next generation of empiricists will pick up and swing until the floor gives way.
Chapter 3
The two kinds of quality, and the honest ceiling
"The ideas produced in us by these secondary qualities have no resemblance of them at all. There is nothing like our ideas, existing in the bodies themselves."
Having shown how the mind fills, Locke asks how much of what fills it is really out there in the world, and his answer splits the qualities of objects in two. Some qualities, he says, an object has in itself, whether or not anyone perceives it. These are the primary qualities: "solidity, extension, figure, motion or rest, number." Its bulk, its shape, the space it takes up, whether it is still or moving, how many of it there are: these belong to the body and stay put when everyone looks away. The idea the mind forms of a thing's shape genuinely resembles the shape the thing has.
The other kind is where the surprise lives. Secondary qualities are color, sound, taste, smell, warmth, the ones that seem just as solidly in the object as its shape. Locke argues they are not. A secondary quality is not a feature sitting in the body the way redness seems to sit in an apple; it is only a power the body has, by means of its primary qualities (the texture and motion of its tiny parts), to produce a certain sensation in a perceiver. The redness is not in the apple waiting to be seen. The apple has a surface that, under light, in an eye built like a human eye, causes the sensation of red; in the dark there is no red, only the surface. And the crucial blow: the ideas these secondary qualities produce "have no resemblance of them at all. There is nothing like our ideas, existing in the bodies themselves." The shape-idea resembles the shape; the red-idea resembles nothing in the apple. Half of what the senses report back about the world turns out to be partly the mind's own contribution.
Locke's own demonstration is a basin of water. A person warms one hand at a fire and cools the other in snow, then plunges both into the same basin of tepid water. The one hand reports the water as cold, the other reports the very same water as warm. The water cannot be both at once; the warmth and the cold are not sitting in the water, since the water has only one state. What is in the water is a certain motion of its parts, a primary fact; the warmth and the cold are sensations the water has the power to produce, and which one a person feels depends on the hand, not the water. Color, taste, sound, smell all go the same way. The world the senses paint is a collaboration, and the brighter half of the colors is supplied by the painter.
This is exactly the crack the next thinker walks through. Berkeley, in the following generation, accepted Locke's argument that secondary qualities exist only in the perceiving and then asked the obvious question Locke had not pressed: why stop there? If the redness is only in the mind, why is the shape any different, given that the shape too arrives only as an idea, only as something seen or felt? Locke had conceded half the world to the mind; Berkeley took the rest. But that is Berkeley's move, and Locke himself does not make it; he holds the line at primary qualities, insisting the shape really is out there even as the color is not.
Where Locke does press, in the Essay's final book, is on the limits of the whole enterprise, which the textbook caricature of cheerful common-sense Locke leaves out. He does not claim that experience yields certainty about everything. Knowledge in the strict sense, he holds, is the mind's perception of how its own ideas agree or disagree, so it reaches exactly as far as our ideas reach and no further. About the deep inner nature of things, the substance supposed to underlie all the qualities and hold them together, Locke confesses we have no clear idea at all; it is, in his phrase, a "something, I know not what." We perceive the qualities; the stuff beneath them, if there is any, is hidden. And our knowledge of the external world, and of other minds, and of the future, is at best probable, never demonstrative; we have good reason to trust it and no proof of it. The man who founded the philosophy of experience set its ceiling himself, with his own hand, and set it low. That honesty about how little we can be certain of is not a weakness in the system. It is the system's nerve, and the heir who took it most seriously was Hume.
Chapter 4
Free, equal, and owed nothing: the state as a trust
"Men being, as has been said, by nature all free, equal, and independent, no one can be put out of this estate, and subjected to the political power of another, without his own consent."
The same year, off the same desk, came the politics, and it runs on the same instinct: refuse the thing handed down as given, and ask what it actually rests on. The first of the Two Treatises is a demolition, a point-by-point attack on Sir Robert Filmer's Patriarcha, which argued that kings rule by divine right inherited from the fatherly authority God gave Adam. Locke takes that apart (no such descent can be traced, and fatherhood would not confer political rule in any case) and then, in the far more important Second Treatise, builds the alternative from the ground up. If authority does not come down from Adam, where does it come from? To answer, Locke does what Hobbes had done a generation earlier: he imagines people with no government at all, the state of nature, and asks what they are owed and what they would do.
Hobbes's state of nature was a war of every man against every man, life solitary, poor, nasty, brutish, and short, which is why Hobbes concluded that people must hand all their power, irrevocably, to an absolute sovereign who makes no promises in return. Locke read the same human material and drew nearly the reverse. His state of nature is not a war. It is "a state of perfect freedom" in which people order their actions "within the bounds of the law of nature," and it is equally "a state... of equality, wherein all the power and jurisdiction is reciprocal, no one having more than another." There is a moral law in force even with no police to enforce it, a law of nature knowable by reason, and its core command is plain: "no one ought to harm another in his life, health, liberty, or possessions." People hold rights before any government exists, not as a gift from the state but because reason discloses the law and, Locke adds, because each person is the workmanship of one maker and so no one's to destroy. The rights come first; the state comes after.
Before the state arrives, Locke has to explain how anyone owns anything, since the earth was given to mankind in common, and his answer is the labour theory of property. A man may not own the common world, but he owns himself, and therefore owns his own labour. "The labour of his body, and the work of his hands, we may say, are properly his." When he takes something out of the common store and mixes his labour with it, picks the apple, tills the field, draws the water, "he hath mixed his labour with, and joined to it something that is his own, and thereby makes it his property." Property is thus pre-political: it is made by work, not granted by a ruler, which means a government that seizes it is taking what was never the government's to give. That single argument, property earned by labour and held against the state, runs straight into the heart of later economics and politics.
So why leave the state of nature at all, if it is free and not a war? Because, Locke says, the enjoyment of one's rights there is "very uncertain, and constantly exposed to the invasion of others." The trouble is not violence but the lack of an impartial referee: with no shared judge, every person must defend his own rights and punish his own wrongs, and people judge their own cases with a heavy thumb on the scale. So people consent to set up a government, joining together "for the mutual preservation of their lives, liberties and estates, which I call by the general name, property." "Men being... by nature all free, equal, and independent, no one can be put out of this estate, and subjected to the political power of another, without his own consent." Authority does not descend from above; it is authorized from below, by the agreement of the governed.
What the people set up is not a master but a trustee. Where Hobbes's sovereign promised nothing and could not be called to account, Locke's government is hired for a specific job, the protection of the rights people already had, and is bound by the terms of that job. The power stays, in the end, with the people who lent it. And from the trustee model follows the conclusion that put Locke's name in danger: the right of revolution. When legislators "endeavour to take away, and destroy the property of the people, or to reduce them to slavery under arbitrary power," Locke writes, "they put themselves into a state of war with the people, who are thereupon absolved from any farther obedience." A government that attacks the very lives, liberties, and property it was trusted to guard has broken the trust and forfeited the power; it "devolves to the people," who may dissolve it and build a new one. Locke's own name for that last resort, when a tyrant has put himself in a state of war and no earthly judge can settle it, is the appeal to heaven. A century later the same frame, life and liberty and property, government by consent, the right to throw off a ruler who turns predator, would be lifted almost whole into the American Declaration of Independence, with Jefferson swapping Locke's "estate" for "the pursuit of happiness" and writing "consent of the governed" where Locke had written consent of the people.
Chapter 5
The wall between the sword and the soul
"The commonwealth seems to me to be a society of men constituted only for the procuring, preserving, and advancing their own civil interests."
The third book of 1689 is the shortest and in its way the most immediately practical, because it addressed the thing that had been tearing Europe apart for a hundred and fifty years: religious persecution, the conviction that a state must enforce the true faith and stamp out the false ones. Locke had grown up in the long aftermath of wars of religion and had watched, from inside government, how a state that policed belief made enemies of its own people. The Letter Concerning Toleration, written in Latin during his exile and translated into English by his friend William Popple, makes the case for getting the magistrate out of the business of souls, and it does so by an argument, not a plea for niceness.
The argument begins by fixing what a government is actually for. "The commonwealth," Locke writes, "seems to me to be a society of men constituted only for the procuring, preserving, and advancing their own civil interests." Civil interests are the things of this world: life, liberty, health, property. That is the magistrate's whole jurisdiction, and the care of souls is simply not on the list, because it is a different kind of business altogether. The state's instrument is force, and force is the wrong tool for the job, which is the crux of the whole Letter.
Force is the wrong tool for the job, because the end of religion is genuine belief, the inward assent of the mind to what it takes to be true, and "such is the nature of the understanding, that it cannot be compelled to the belief of anything by outward force." A magistrate can make a man attend a church, recite a creed, and bow at the right moments, on pain of fine or prison. What the magistrate cannot do is make the man actually believe it, because belief follows what the mind finds convincing, not what the body is threatened with. Coercion can manufacture a hypocrite; it cannot manufacture a believer. So persecution, even on its own terms, fails: it cannot deliver the genuine faith it claims to be protecting, and it ends only in outward conformity and inward resentment. The sword and the soul operate by different laws, and the one can get no purchase on the other.
It would flatter Locke to leave it there, and the honest account does not. His toleration had hard edges, drawn by the anxieties of his own moment. He did not extend it to atheists, on the ground that someone who denies God can give no binding force to an oath or promise, so the bonds of society have no hold on him; a man who believes nothing sacred, Locke thought, cannot be trusted to keep his word, and a society runs on kept words. And he was wary of Catholics, not for their theology as such but because he saw them as owing allegiance to a foreign power, the Pope, which to Locke made them a civil threat rather than merely a religious minority. The wall between the sword and the soul, in Locke's own building of it, had gates in it for the people he thought dangerous to the state. The principle he stated was larger than the version he was willing to apply, and later generations would hold him to the principle, widening the toleration until it covered the very people he had left outside.
Chapter 6
The blank page and its blind spot
"Every freeman of Carolina shall have absolute power and authority over his negro slaves."
Locke's reach is hard to overstate, and it runs in two directions at once, because the two books of 1689 founded two different things. The Essay founded British empiricism, the line of thought that the next century carried to its limit. Berkeley took Locke's split between primary and secondary qualities and pushed it past where Locke would go, dissolving mind-independent matter entirely. Hume inherited the whole empiricist program, Locke's starting rule that every idea must trace to experience, and ran it without mercy until it dissolved causation, the self, and the rational warrant for expecting tomorrow to resemble today. The modest physician who said the mind is white paper set in motion the argument that ended, three generations later, with Hume showing that experience cannot even ground the sunrise.
The other direction is political, and it shaped not a school but a country. The Two Treatises gave the eighteenth century its working theory of legitimate government: rights that exist before the state, power that rises from the consent of the governed, a ruler who holds his authority on trust, and a people entitled to take it back when the trust is broken. When the American colonists came to justify their break with Britain, they reached for Locke almost word for word, life and liberty and property, government by consent, the right to throw off a tyrant. He is, with as much justice as the phrase ever carries, a founder of modern liberalism, the tradition that puts individual rights and limited, consenting government at the center of politics.
And the man who taught the West to ask what any belief is grounded in did not turn that question on one of his own. Locke was an investor in the Royal African Company, the English crown's monopoly on the Atlantic slave trade, holding stock from which he stood to profit by the buying and selling of human beings. He was also, as secretary to the Lords Proprietors of Carolina, involved in drafting the Fundamental Constitutions of Carolina of 1669, the colonial charter that entrenched hereditary slavery and declared that "every freeman of Carolina shall have absolute power and authority over his negro slaves." How much of that specific clause came from Locke's own pen is genuinely disputed among scholars; that he was the document's secretary and had a hand in its drafting, and that he profited from the slave trade, is not.
The point is not to catch a hypocrite and move on; it is more uncomfortable than that. The same Locke who wrote that all men are by nature free and equal, that no one may harm another in his life, liberty, or possessions, and that no one may be subjected to political power without his own consent, was at the same time an investor in, and a legal architect of, a system that treated certain people as property and asked no one's consent at all. "All men" in his hands covered a far narrower set of people than the words say, with the enslaved and the indigenous simply outside the circle. This is part of the intellectual record, not a footnote to it, and it traveled with the theory: the American founders borrowed Locke's frame of universal natural rights at the very moment American slavery was expanding, and the same gap between the words and their reach traveled with the words. The fork Locke ran so relentlessly over innate ideas and divine right, demand the receipt, check it against the facts, discard what rests on nothing, he never once ran over this.
What the careful physician left behind, then, is a single instinct applied to the two largest questions there are, and applied unevenly. Take nothing on authority; ask what it rests on; build only on what the evidence will actually bear. He turned that demand on the furnished mind and emptied it to white paper, founding the philosophy of experience and setting it an honest ceiling. He turned it on the divinely-appointed king and dissolved him into a hired trustee, founding the politics of consent and the right to revolt. He turned it on the persecuting state and walled it out of the conscience. And he did not turn it on the slave ship he owned a share in, which is the measure both of how powerful the instrument was and of how human the hand that held it. He gave the modern world a way to ask whether a belief or a government has any right to the obedience it demands, and the first thing that way of asking does, used honestly, is convict the man who built it.