Representing the consolidation, as distinct from total merger, of two religious traditions, the Unitarian Universalist Association (UUA) is a religious organization formed in 1961. Its constituents are the Universalists, who organized in 1793, and the Unitarians, who organized in 1825.
While it derives from Judaeo-Christian traditions (see Source 4), it is not considered Christian since Unitarianism rejects the concept of the Trinity, and thus the Christ. It explicitly accepts humanists and followers of earth-centered spirituality, and does not require belief in a deity.
As a religion, Unitarian Universalism has no specific doctrine (i.e., "creed"), but rather the set of values of affirming the worth of human beings, advocating freedom of belief and the search for advancing truth, and providing "a warm, open, supportive community for people who believe that ethical living is the supreme witness of religion." The values break into:[1]
While the idea of a single Godly entity was held by some early Christians, assuming Jesus was human, the Council of Nicea declared this heresy in 325 CE, and the doctrine of the Trinity established. Universal salvation was rejected by an ecumenical council in 533 CE.
During the Reformation in the sixteenth century, these doctrines were challenged. The first Unitarian churches were established in Transylvania by Francis David, and spread through Europe. Joseph Priestley, in 1794, started the first Unitarian church in North America.
In parallel, churches with the idea of universal salvation spread in America, the first being started by John Murray in 1780.
Another concept, transcendentalism, began approximately 1840, holding that individuals could have direct experience of the divine and unity with nature, and a duty to address social issues. Ralph Waldo Emerson and Theodore Parker formed these ideas.