Leland, John (1691–1766), presbyterian minister, was born 18 October 1691 in Wigan, Lancashire, England, second of three sons of a presbyterian merchant, whose name was possibly William Leland; there are no firm details of his mother. After suffering from smallpox at the age of five or six, the boy was apparently brain-damaged and completely lost his memory; when he recovered after a year he had to learn everything afresh. Not long afterwards the father failed in business, surrendered all his effects to creditors, and moved with his family to Dublin to start again. John made such good progress at school that he was given a private tutor in philosophy, and local ministers supervised him in Hebrew and divinity. In 1716 he received a unanimous call to be joint minister with Nathaniel Weld (1660–1730) in New Row congregation, Dublin, which moved after 1725 to a new site in Eustace St. In 1733 Leland published an attack on Matthew Tindall's deistical work Christianity as old as creation ... (1730), and in the late 1730s he carried on a published controversy with Dr Thomas Morgan, another deist. One of Leland's books, published in 1740, was translated into German in 1756. In 1734 he was awarded an MA degree by the University of Glasgow; in 1739 he received a DD from King's College, Aberdeen.
A group of influential authors and divines sought his assistance in combatting the spread of deistical ideas, seen as a very real threat to Christianity; ‘rational religion’, as espoused by writers such as David Hume and Henry St John Bolingbroke, was regarded by these men as a stalking-horse for infidelity. Leland's A view of the principal deistical writers that have appeared in England during the last and present century appeared in three volumes (1754–6) and had several editions over the next hundred years. It was regarded as a useful compilation of the arguments for and against deism, and with other works, including The advantage and necessity of the Christian religion ... (1764), secured for Leland a considerable reputation among clergy of the established church, as well as in the dissenting tradition. An annuity purchased with all the profits from the work turned out to be valueless, thanks to its vendor's trickery.
Leland took no part in the subscription controversy of the day and was not much concerned with detailed expositions of Scripture, but was a clear and committed preacher. He almost died in a serious feverish illness when he was 70, but on recovery his general health was so much improved that he regarded it as a providential intervention to allow him to complete his life's work in defence of Christianity. A neglected cold led to his death in Eustace St. on 16 January 1766.
He married (10 May 1731) Ann Macquay in St Nicholas Without, Dublin; she was the widow of Thomas Macquay (d. 1729), who had been a minister in Dublin and Leland's friend since their student days. Leland was a second father to his stepchildren; his own children (it is not known how many) all died young. The historian Thomas Leland (qv) was probably a nephew. Two members of the Macquay family appear to have been named after Leland: John Leland Macquay (1759?–1829), merchant and governor of the Bank of Ireland, and his nephew John Leland Macquay (1791–1868), an important figure in the anglophone community in Florence, whose journals and papers form an important historical source.