Unitarianism, unorthodox Protestant faith that rejects the Trinity and the divine nature of Christ, and asserts the unipersonality of God. It developed out of views of such Reformation figures as Faustus Socinus, who influenced many 18th-century English Presbyterians to become Unitarians. Joseph Priestley gave it a great impetus in the United States, where liberal, rationalist Unitarianism, preaching toleration and universal salvation, developed among Congregational churches. The American Unitarian Association, led by William Ellery Channing, was founded in 1825. In 1961 the Unitarian and Universalist churches merged, creating the Unitarian Universalist Association.
See also: Protestantism.