Born in county Donegal,Ireland, he emigrated to the United States in 1815 with his widowed mother and her eight other children. Already a local preacher, he entered the ministry of the Ohio Conference of the Methodist Episcopal Church. Throughout his ministry he valued contacts with Ireland. Highlights in a distinguished ministry included being superintendent of missions among the Wyandotte Indians, professor of Ancient Languages in Madison College, Pennsylvania (1827-1831); editor of the Western Christian Advocate for long periods in the 1830s to 1850s, and of the Central Christian Advocate from 1860; and professor of Biblical Literature, then President in the Iowa Wesleyan University between 1856 and 1860.
A prolific writer, his editorials were widely read. They were strongly opposed to slavery, Roman Catholicism and reservations for American Indians. The Sinfulness of American Slavery was published in 1850. Though acknowledging that 'mild and moderate' slave-holders might show benevolence towards their slaves, he argued that this did not modify 'the incurable evils' of slavery. His Delineation of Roman Catholicism, first published in two volumes in 1841 and running to several editions, was widely known on both sides of the Atlantic. He also published A History of the Great Secession (1852).