With the exception of the abstract of the Essay and other less important contributions to the Bibliothèque universelle, Locke had not published anything before his return to England in 1689; and, by this time, he was in his fifty-seventh year. But many years of reflection and preparation made him ready now to send forth books from the press in rapid succession. In March, 1689, his Epistola de Tolerantia was published in Holland; an English translation of the same, by William Popple, appeared later in the same year, and, in a corrected edition, in 1690. The controversy which followed this work led, on Locke’s part, to the publication of a Second Letter, and then of a Third Letter, in 1690 and 1692 respectively. In February, 1690, the book entitled Two Treatises of Government was published, and in March of the same year appeared the long expected Essay concerning Human Understanding, on which he had been at work intermittently since 1671. It met with immediate success, and led to a voluminous literature of attack and reply; young fellows of colleges tried to introduce it at the universities, and heads of houses sat in conclave to devise means for its suppression. To one of his critics Locke replied at length. This was Edward Stillingfleet, bishop of Worcester, who, in his Vindication of the Doctrine of the Trinity (1696), had attacked the new philosophy. It was the theological consequences which were drawn from the doctrines of the Essay not so much by Locke himself as by Toland, in his Christianity not mysterious, that the bishop had chiefly in view; in philosophy for its own sake he does not seem to have been interested. But his criticism drew attention to one of the least satisfactory (if, also, one of the most suggestive) doctrines of the Essay—its explanation of the idea of substance; and discredit was thrown on the “new way of ideas” in general. In January, 1697, Locke replied in A Letter to the Bishop of Worcester. Stillingfleet answered this in May; and Locke was ready with a second letter in August. Stillingfleet replied in 1698, and Locke’s lengthy third letter appeared in 1699. The bishop’s death, later in the same year, put an end to the controversy. The second edition of the Essay was published in 1694, the third in 1695, and the fourth in 1700. The second and fourth editions contained important additions. An abridgment of it appeared in 1696, by John Wynne, fellow of Jesus college, Oxford; it was translated into Latin and into French soon after the appearance of the fourth edition. The later editions contain many modifications due to the author’s correspondence with William Molyneux, of Trinity college, Dublin, a devoted disciple, for whom Locke conceived a warm friendship. Other correspondents and visitors to Oates during these years were Sir Isaac Newton and Anthony Collins, a young squire of the neighbourhood, who afterwards made his mark in the intellectual controversies of the time.
Other interests also occupied Locke during the years following the publication of his great work. The financial difficulties of the new government led, in 1691, to his publication of Some Considerations of the Consequences of the Lowering of Interest, and Raising the Value of Money, and of Further Considerations on the latter question, four years later. In 1693, he published Some Thoughts concerning Education, a work founded on letters written to a friend, and, in 1695, appeared The Reasonableness of Christianity, and, later, A Vindication of the same against certain objections; and this was followed by a second vindication two years afterwards. Locke’s religious interest had always been strongly marked, and, in the later years of his life, much of his time was given to theology. Among the writings of his which were published after his death are commentaries on the Pauline epistles, and a Discourse on Miracles, as well as a fragment of a fourth Letter on Toleration. The posthumously published writings include, further, An Examination of Father Malebranche’s Opinion of Seeing all things in God, Remarks on Some of Mr. Norris’s Books, and—most important of all—the small treatise on The Conduct of the Understanding, which had been originally designed as a chapter of the Essay.