A denomination of the Christian Church which rejects the doctrine of the Trinity. One of the Protestant sects that developed out of the Reformation, it is found under various names, first in Poland in the second half of the sixteenth century, and a little later in Transylvania, where it still flourishes, although its modern center of gravity is England and the other English-speaking countries, notably the United States. Exclusion from Protestant synods crystallized the Unitarians into a separate church in 1565. Among its prominent exponents may be mentioned the elder and the younger Socinus, who formulated its first theology; Francis David, its first martyr; and Joseph Priestley, the English discoverer of oxygen. It also claims Milton, Locke, and Newton, and it owes much to James Martineau, who rationalized the crudities of Priestley's theology, while Emerson gave it its transcendental touch and the writings of Channing and Theodore Parker furthered its propaganda.
From its inception this sect has been divided into conservative and radical wings. In the former school the divinity of Jesus is rejected, but the miracles ascribed to him are accepted, and some regard him as preexistent and superangelic. Socinus insisted on his worship. In the new, or radical, wing of Unitarianism, Jesus is still sublimated above all humanity, while the cross, the symbol of the whole of Christianity, is accepted metaphorically as expressed in poetry and hymnal. The Lord's Supper is observed as a commemoration, thus uniting Unitarianism with the whole Church. For about fifteen centuries, accordingly, Unitarianism has been historically linked with Christianity, from which it has never entirely broken away. The Apostles, the Church Fathers, and the Holy Roman Empire are its remote progenitors. More specifically, its progressive steps may be traced from the Arian movement through Calvinism, Socinianism, Arminianism, Presbyterianism, and Congregationalism, the Hicksite Quakers and the Universalists occupying parallel places. Unitarianism has, therefore, been a development out of Trinitarianism. Gradually the Holy Ghost was rarefied into an "influence," and the Son of God was explained away as a figure of speech. The preponderating influence of the parent faith, however, still abides, and the Unitarians do not look upon the character of Jesus in the cold light of history.