John Locke

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John Locke was the English philosopher and physician whose Essay Concerning Human Understanding (1690) argued that the mind begins as blank paper, owing every idea it holds to experience — the founding statement of British empiricism, and the book that set the terms on which the following centuries would judge claims of inward illumination. In the history of Western esotericism Locke matters chiefly from the outside, as the architect of the tribunal before which such claims were thereafter summoned; yet his own circle places him closer to the laboratory than the reputation suggests.

The book against innate ideas

The Essay opens not with a doctrine but with a demolition. Book I sets out to clear the ground of innate ideas — the supposition, common to the schools and dear to the Cambridge Platonists, that certain truths are stamped on the soul from birth, prior to all experience. Locke’s case is patient and corrosive. If a principle were truly innate, it would be universally assented to; but children and the unschooled assent to no such principles, and there is no proposition — not the law of identity, not the rule that the whole is greater than the part, not the existence of God, not the prohibitions of the moral law — that all minds acknowledge. Universal consent, the only evidence ever offered for innateness, fails the test of fact. And if the reply is that innate truths lie latent until reason draws them out, then innateness has done no work: whatever reason can discover needs no prior stamping, and the doctrine collapses into the very empiricism it was meant to forestall.

What Book I clears away, the rest of the Essay fills back in from below. Every idea the mind possesses arrives by one of two doors — sensation, the report of the outer senses, and reflection, the mind’s observation of its own operations. The newborn understanding is, in the figure that became the book’s emblem, white paper void of all characters. From the simple ideas these two sources deliver, the understanding compounds, abstracts, and relates, but it adds no original content of its own. The architecture is deliberately modest, and the modesty is the point: Locke is drawing the bounds of knowledge to keep the understanding from spending itself on questions it has no instruments to settle. The famous image of the sailor with a sounding line — who need not fathom the ocean’s depth, only know where the shoals are that would wreck him — governs the whole. Where the rationalist trusted clear and distinct ideas planted in the mind by God, and where Gassendi had already turned the revived atomism of Epicurus against innatism a generation before, Locke built the empiricist tribunal that would, a century on, give Kant the problem of his life: how the mind, if it begins empty, can possess any knowledge that is both necessary and about the world.

Of enthusiasm: the mark revelation owes

Into the fourth edition of 1700 Locke inserted a short chapter that would do more to shape the reception of mysticism than anything else he wrote: “Of Enthusiasm.” Its target was the sectary — the man of the previous, war-torn century who claimed an immediate light, a private revelation bypassing both scripture and reason — but its reach was general. Locke does not deny that God may speak directly to a mind. He demands only this: that anyone who claims it owes some mark by which true revelation can be distinguished from the strong persuasion that something is revealed. The felt strength of a conviction is not that mark. A man may be as certain as he likes that his impulse comes from above; certainty about the impulse is not evidence about its source. Firmness of belief proves only the firmness, not the truth — to be sure that one is in the right because one is sure is to reason in a circle that admits any enthusiasm whatever.

The chapter installs a permanent demand at the threshold of every claim to direct knowledge of the divine. After Locke, the burden lies on the visionary, not on the skeptic: inner light must produce credentials that reason can read, or stand unjudged and unjudgeable. This is the frame within which European thought has received private revelation, prophetic vocation, and the whole literature of illumination ever since — not refuted, but quarantined behind a question it cannot answer in its own terms. That the chapter sits inside a book otherwise devoted to the limits of the understanding is no accident: enthusiasm, for Locke, is exactly the understanding overreaching its sounding line, mistaking the heat of its own assent for a message from outside the room.

The demand is the more pointed because Locke had already drawn the map of where revelation may legitimately sit. Some propositions are according to reason, agreeable to what the understanding can establish on its own; some are above reason, beyond what it can reach but not against it — and these are revelation’s proper province; some are contrary to reason, and these no purported revelation can carry, because the evidence that any message is from God can never outweigh the evidence of a plain absurdity. Revelation, in this scheme, is not abolished but ranked: it cannot overturn what reason knows clearly, and even where it speaks above reason it must first prove itself a genuine revelation, which is precisely the credential enthusiasm cannot supply. The visionary who feels the truth of his light has, on Locke’s terms, mistaken a sensation for an argument.

A lean Christianity

Locke’s own theology ran spare, and ran toward the same threshold. The Reasonableness of Christianity, as Delivered in the Scriptures (1695) set out to find the minimum a man must believe to be a Christian, and reduced it, after a long reading of the Gospels and Acts, to a single proposition: that Jesus is the Messiah. Faith and works follow, but the saving article is that one. The economy was deliberate — a creed stripped to what scripture plainly required, designed to make belief possible for the unlearned and to drain the doctrinal disputes that had fed a century of bloodshed. It scandalized the orthodox at once. John Edwards charged the book with Socinianism — the anti-Trinitarian current that denied the eternal deity of Christ — and Locke answered with two Vindications, denying the label without ever affirming the Trinity he was accused of dropping. What he privately held about the three persons of the Godhead is argued to this day; his surviving notes are guarded, his published silence exact. The pattern is the same one the Essay prescribes: where the evidence does not reach, suspend the assent. The doctrines he would not affirm he also would not deny.

This places Locke at the edge of a current that ran on after him through John Toland — whose Christianity Not Mysterious (1696) pushed the reasonable-religion program past anything Locke would own, into a deism that left no room for mystery at all — and on toward the radical critics who would dismantle revealed religion entirely. Locke held a line Toland did not: revelation, properly attested, remained for him a genuine source of truth above reason, and the Letter Concerning Toleration (1689) had already argued that civil power has no business compelling belief — though Locke drew his own boundary at atheists, whose oaths he thought no society could trust, and at Catholics, whose allegiance he judged divided.

Wrington to Oates

He was born at Wrington in Somerset in 1632, the son of a country attorney who had ridden for Parliament in the civil war. A scholarship carried him to Westminster School, and from there to Christ Church, Oxford, where he took his degrees, lectured, and read the new corpuscular natural philosophy with more appetite than he ever showed for the Aristotelian curriculum. He turned to medicine and made it the discipline of his mind before it was his profession. He studied under and worked alongside Thomas Sydenham, the great clinical empiricist of the age, and absorbed from him a method that distrusted system and grand hypothesis and held to careful observation of what the patient actually presented — the same temper that would govern the Essay. He never took the formal medical degree, and it was medicine all the same that changed his life: summoned to treat Anthony Ashley Cooper, the future first Earl of Shaftesbury, he supervised an operation to drain a liver abscess, fitting a silver tube to keep the wound open, that saved the patient, and entered his household as physician, secretary, and adviser. He served the rising Whig statesman through the politics of exclusion and the Popish Plot. When Shaftesbury’s opposition collapsed and the patron fled, Locke followed into exile, withdrawing to the Netherlands in 1683 and moving under an assumed name while his Oxford studentship was stripped from him by royal order. He returned only after the revolution of 1688, crossing in the convoy that carried the future Queen Mary.

The great works then arrived almost at once — the Essay, the Two Treatises of Government, the Letter Concerning Toleration — most of them published anonymously, their authorship an open secret Locke acknowledged only at his death. His last years were spent at Oates in Essex, in the manor of Sir Francis Masham, where he lived from 1691 as a permanent guest. The household was that of Damaris, Lady Masham — daughter of Ralph Cudworth, the Cambridge Platonist, and a philosopher in her own right, who corresponded with Leibniz and wrote her own defenses of a rational, ethically demanding Christianity. He died there in February 1704, asthmatic and failing, while she read the Psalms aloud to him.

The friend of the laboratory

There is an irony in that deathbed. The first book of the Essay had dismantled the innate ideas the Cambridge school existed to defend; Cudworth’s True Intellectual System of the Universe (1678) had labored to prove the soul’s native possession of eternal moral truths and a divine Plastic Nature ordering the world from within — and Locke died under the roof of Cudworth’s daughter, who knew the Essay well enough to press him on it in their letters. The disagreement was real and the affection survived it.

It survived because Locke was never simply the dry adjudicator of his reputation. He stood, all the while, inside the same network as the private Newton — the network of the Royal Society, to which he was elected Fellow in 1668, and of Robert Boyle, whom he had known since his Oxford years and whom he regarded as a master. When Boyle died in 1691, Locke saw his unfinished General History of the Air through the press the following year, an editor’s labor of piety. Portions of an alchemical process Boyle had guarded — a recipe for the increase of gold, divided among three trustees so that no one held the whole — passed to Locke as one of those trustees. In the summer of 1692 he wrote to Newton about it, and Newton wrote back at length about the red earth and the mercury the process required, urging caution and secrecy in the same breath that he confessed his own years at the furnace. The correspondence is one of the few places where the two greatest English minds of the age speak to each other as fellow initiates of a discipline both kept hidden from the world that knew them as the author of the Essay and the author of the Principia.

Two years before that, in 1690, Newton had trusted Locke with a different secret: a manuscript — later printed as An Historical Account of Two Notable Corruptions of Scripture — arguing that the two great proof-texts of the Trinity were later interpolations, corruptions of the original text. Newton meant it for anonymous publication abroad through Locke’s Dutch contacts, then took fright and withdrew it. Locke kept the confidence. On the evidence of the letters, he handled all of these materials — the guarded recipe, the heretical philology, the dead friend’s papers — much as the Essay would predict: curious, exact, and unpersuaded.

Sources and scholarship

The modern critical foundation for Locke’s life is Maurice Cranston’s John Locke: A Biography (1957), supplemented and in places corrected by Roger Woolhouse’s Locke: A Biography (Cambridge University Press, 2007), which draws on the full archive Peter Laslett identified at the Bodleian. The standard text of the philosophy is the Clarendon Essay, edited by Peter H. Nidditch (1975); the Clarendon Edition of the Works, in progress, supersedes the older collected editions. Locke’s first book is now searchable in full through the EEBO-TCP keyed transcription of the early editions, hosted open-access at quod.lib.umich.edu.

Locke’s relation to the Cambridge Platonists he both befriended and refuted is best approached through their own texts, several of which are edited online by the Cambridge Platonism Sourcebook, the Cambridge AHRC project directed by Douglas Hedley; Cudworth’s True Intellectual System (1678), the great anti-mechanist defense of innate moral order against which the Essay’s first book reads as a direct reply, is available in the EEBO-TCP transcription at quod.lib.umich.edu. On the theology, John Marshall’s John Locke: Resistance, Religion and Responsibility (Cambridge University Press, 1994) and Victor Nuovo’s editions of the religious writings set the Reasonableness and the Socinian controversy in their context; the philosophical anatomy of “Of Enthusiasm” and Locke’s account of faith and reason is treated in Nicholas Wolterstorff’s John Locke and the Ethics of Belief (Cambridge University Press, 1996). The chemical and alchemical strand — the Boyle trusteeship and the 1692 exchange with Newton over the red earth — is documented in Lawrence M. Principe’s The Aspiring Adept: Robert Boyle and His Alchemical Quest (Princeton University Press, 1998) and in the volumes of The Correspondence of Isaac Newton edited by H. W. Turnbull. The continuity from Locke’s reasonable Christianity to its more radical heirs runs through John Toland and, beyond him, into the deist controversy; the longer trajectory of the ancient-wisdom debate the Cambridge men contested is traced under Prisca Theologia.

→ Related: Isaac Newton · Cambridge Platonism · Henry More · Gottfried Wilhelm Leibniz · Rene Descartes · Empiricism · Revelation · Reason · Mysticism · Royal Society · Alchemy · Pierre Gassendi · Immanuel Kant · John Toland · Giordano Bruno · Prisca Theologia