His main principle was a rigid unitarianism which denied the independent existence of the attributes of God, as being incompatible with his unity, and therefore a polytheistic idea.
This view has, however, made but little way in England and America, where the opinions of the great majority of spiritualists vary from orthodox Christianity to Unitarianism of an extreme kind.
But the Unitarianism of those times, even the Unitarianism of Channing, was very different from that of to-day.
He was an able controversialist, and in the interests of Arminianism attacked both New England Calvinism and Unitarianism; he published in 1837 The Calvinistic Controversy.
In the volume Unitarianism Defended, 1839.
At Litchfield and in Boston he was a prominent opponent of the $rowing "heresy" of Unitarianism, though as early as 1836 he was accused of being a "moderate Calvinist" and was tried for heresy, but was acquitted.
That modern Unitarianism is all to be traced back to Sozzini and the Rakow Confession need not be assumed.
He returned to America in 1840, was a tutor for a few months (1840-1841) at Bowdoin, and in 1842, shut out from any better place by distrust of his German training and by his frank opposition to Unitarianism, he became pastor of the Congregational Church of West Amesbury (now Merrimac), Massachusetts.
A number of them find in Unitarianism a form of Christianity that appeals to them.
He at once began to take an independent part in the movements then agitating NewEngland, which between 1830 and 1850 was stirred by discussions pertaining to Unitarianism, transcendentalism, spiritualism, abolitionism and various schemes for communistic living.
He looked on Unitarianism with much sympathy and desired its growth.
William Frend, a fellow of Jesus, accused of sedition and Unitarianism, was at this time tried and expelled from Cambridge.
As Carlyle has told in his Life of Sterling, the poet's distinction, in the eyes of the younger churchmen with philosophic interests, lay in his having recovered and preserved his Christian faith after having passed through periods of rationalism and Unitarianism, and faced the full results of German criticism and philosophy.
Between pantheism and Unitarianism he seems to have balanced till his thirty-fifth year, always tending towards the former in virtue of the recoil from "anthropomorphism" which originally took him to Unitarianism.
After giving up Unitarianism he claimed that from the first he had been a Trinitarian on Platonic lines; and some of his latest statements of the doctrine are certainly more pantheistic than Christian.
His principal published works are: Stories from the Life of the Teacher (1863), A Child's Book of Religion (1866), and other works of religious teaching for children; several volumes of sermons; Beliefs of Unbelievers (1876), The Cradle of the Christ: a Study in Primitive Christianity (1877), The Spirit of New Faith (1877), The Rising and the Setting Faith (1878), and other expositions of the "new faith" he preached; Life of Theodore Parker (1874), Transcendentalism in New England (1876), which is largely biographical, Gerrit Smith, a Biography (1878), George Ripley (1882), in the "American Men of Letters" series, Memoir of William Henry Channing (1886), Boston Unitarianism, 1820-1850 (1890), really a biography of his father; and Recollections and Impressions, 1822-1890 (1891).
In this address Emerson laid his hand on the sensitive point of Unitarianism, which rejected the divinity of Jesus, but held fast to his supreme authority.