William Cleghorn was born and died at Edinburgh, where his family were brewers. Through his mother, Jean Hamilton, he was related directly to another leading family, prominent in the church and in bookselling, and indirectly to the Balfours, prominent in bookselling and the law. A sister-in-law was the daughter of William Scott. Cleghorn attended Edinburgh University in the early 1730s (MA 1739). He trained for the ministry but was never ordained to a charge. In 1742 John Pringle took indefinite leave from the chair of Moral Philosophy and paid for Cleghorn and George Muirhead to conduct his classes. When Pringle resigned in 1745, the town council tried unsuccessfully to draw Francis Hutcheson from Glasgow. In the eventual contest, Cleghorn secured the vote by a 19:12 margin over William Wishart. A staunch Whig and member of the Revolution Club, he joined a volunteer company during the 1745 rebellion, and in 1746 published A Comparison of the Spirit of the Whigs and Jacobites, a discourse delivered to an ‘Audience of Gentlemen in Edinburgh’ in December 1745. His most distinguished pupil was Adam Ferguson, whom he recommended as his successor, but James Balfour, a distant relative, secured the succession on Cleghorn's death.
From The Continuum Encyclopedia of British Philosophy in Oxford Reference.