Campbell's first major publication, "A Dissertation in Miracles" (1762), was directed against David Hume's attack on miracles in "An Enquiry concerning Human Understanding". Campbell was influenced by Hume, but took particular issue with his philosophical strictures. Even though both were in complete opposition over almost every point of philosophy, Campbell and Hume shared a mutual respect. Thanks in part to the success of "Miracles", Campbell became a professor of divinity at Marischal in 1770. He lectured to students to prepare them for the demands of the ministry, both practical and spiritual. Campbell gave lectures on Church history, later published as "Lectures on Ecclesiastical History", and on pastoral character and preaching, later published as "Lectures on Pulpit Eloquence". After completing "The Philosophy of Rhetoric" (1776), Campbell published several sermons and finished his lifelong ambition, "The Four Gospels, Translated from the Greek" (1789).