Between 1660 and 1662 a young tutor at Christ Church, Oxford, wrote two essays arguing that a ruler may lawfully decide how his subjects worship. He was answering Edward Bagshaw, a colleague at the same college, who wanted Protestants outside the national church left alone. The tutor was John Locke, and he had grown up in a civil war. His father, a country lawyer in Somerset, served as a captain in Parliament's cavalry. Locke was a pupil at Westminster School in January 1649, when Charles I was beheaded at Whitehall, a few hundred yards away. He wrote of himself that he had been in a storm for as long as he had known anything.
Those two essays stayed unprinted until 1967, and the books Locke is remembered for argue the other side. One claim runs through all of them: nothing is settled at birth. No idea is in the mind before experience puts it there, and no person is born the subject of another. A doctrine, a church or a king that asks to be obeyed has to show where its authority comes from.
He came to politics through medicine. Oxford taught the philosophy of Aristotle, and Locke found it of little use; what held him was the experimental science of Robert Boyle, the chemist who became his mentor, and the training of a physician. In 1666 Lord Ashley, one of the richest men in England, came to Oxford to drink medicinal waters, met Locke and soon took him into his London household. The next year Locke wrote an essay on toleration that reversed his answer to Bagshaw, and scholars point to his new association with Ashley as the likeliest cause. In 1668 he oversaw an operation that drained an abscess on Ashley's liver, and Ashley credited him with saving his life.
Ashley became Earl of Shaftesbury and led the campaign in Parliament to keep the Catholic heir, the future James II, from the throne. The campaign failed; Shaftesbury fled to Holland at the end of 1682, and Locke left for Holland too in the autumn of 1683. In November 1684 Charles II had him expelled from Christ Church, although the dean reported that nobody in the college had heard him say a word for or against the government. The next year his name stood on a list of eighty-four men whom England asked the Dutch to hand over, and he lived in Amsterdam under the name Dr van der Linden.
He came home in February 1689, after James II had fallen. He was fifty-six and had almost nothing in print. Within a year three books were out. An Essay Concerning Human Understanding, which he signed, argues that every idea comes from the senses or from the mind watching its own workings, so that much of what people call knowledge is well-grounded belief. Two Treatises of Government and A Letter Concerning Toleration, both unsigned, make the matching case about power: rulers hold it in trust from people who consented to it and may be replaced when they break that trust, and no government can force a mind into belief. Locke admitted writing the Two Treatises only in an addition to his will, six weeks before he died.
In 1703 the heads of the Oxford colleges agreed that tutors should not read the Essay with their pupils. The book spread anyway, and the language of the Two Treatises is echoed in the American Declaration of Independence.
The limits Locke set are part of the record too. His toleration left out atheists, and it left out churches whose members owe obedience to a foreign prince, a clause aimed at Catholics. As Ashley's secretary he wrote out the 1669 constitution for the colony of Carolina, which gave every free settler absolute power over his African slaves; historians disagree about how much of it was his own thinking. He also held shares in the Royal African Company, which shipped enslaved people across the Atlantic.