John Cairns (1818-1892), Scottish Presbyterian divine, was born at Ayton Hill, Berwickshire, the son of a shepherd. He entered the Presbyterian Secession Hall in 1840, and in 1843 wrote an article in the Secession Magazine on the Free Church movement, which aroused the interest of Thomas Chalmers. In 1876, he was appointed joint professor of systematic theology and apologetics with James Harper, principal of the United Presbyterian Theological College, whom he succeeded as principal in 1879. He was an indefatigable worker and speaker, and in order to facilitate his efforts in other countries and other literatures he learnt Arabic, Norse, Danish and Dutch. He wrote a long article on Recent Scottish Theology for the Presbyterian and Reformed Review, for which he read over every theological work of note published in Scotland during the preceding half-century. Amongst his other works are: An Examination of Ferrier's Knowing and Being, and the Scottish Philosophy (1856), Memoir of John Brown, DD (1860), Romanism and Rationalism (1863), The Doctrine of the Presbyterian Church (1876), Unbelief in the 18th Century (1881) and Doctrinal Principles of the United Presbyterian Church (1888). His biography is entitled Principal Cairns (1903).