Born, probably in 1730, at Wallacetown in Annandale, where his father was a merchant. He was one of the "four Johns." The first extant minutes of Presbytery, February 9, 1758, gives his name as clerk, a post he retained until his ordination. He was licensed at Crawfordjohn on February 1, 1759, and thereafter spent his probationership in itinerating, once accompanying John M'Millan II to Ireland. On a call from the Societies, he was ordained at Crawfordjohn on May 17, 1762. Along with M'Millan he was apportioned to the Northern congregation on the division of the Church into separate congregations in 1763, and he seems soon to have settled down at Pentland, near Edinburgh, as his home and the centre of his work. In 1787 a definite line was drawn between the district assigned to him and the congregation in the West. He was an earnest student and a diligent pastor. His salary, it is said, never exceeded 20 pounds sterling, but he appears to have had a private income. He did his best to help deserving students, and it is probable boarded suitable men in his manse. His learning was recognised by the proposal in 1785 to make him theological tutor, but he died before arraignments could be carried out. He did not write much. He was the author of the doctrinal part of the Testimony of 1761, an astonishing performance when it is remembered that he was still a probationer. His opus magnum was the Vindiciae Magistratus, written in 1773, in which the divine institution and rights of the Civil Magistrate are vindicated against an Associate Burgher minister. Lord Kames described it as "the best defence of Whig principles." He died on August 17, 1788.