The core of Unitarian Universalist theology has its source in two parallel philosophies: Unitarianism and Universalism. Universalism predates the Common Era, and it is known that many of the early Christian sects were Universalist. That is, they believed in a loving, forgiving god that would accept all good people, regardless of their religious philosophies, into the kingdom of heaven. George de Benneville is often credited with being the first to introduce Universalism to America with his arrival in 1741.
Unitarianism, surfaced in Europe as part of the Reformation in the early to mid 16th century. Unitarianism rejected the concept of the Trinity (Father, Son and Holy Spirit) that had been conceived by the leaders of the Holy Roman Empire in CE 325. Instead, early proponents of Unitarian theology, such as Michael Servetus, declared that there is but one god.
Unitarianism and Universalism existed as separate traditions in the US from colonial times until the mid twentieth century. In 1961 the two churches combined to form the Unitarian Universalist Association (UUA), and many (but not all) congregations also consolidated. Our own congregation, which was initially formed in 1888 as the "First Unitarian Society of Pomona", was re-formed as the "Monte Vista Unitarian Universalist Congregation" in 1962.
While our tradition has its roots in early Christian theology, modern UUs draw inspiration from many religious traditions and sources. We do not require our members to accept any particular creed or belief. However, most UUs would agree that how we live our lives is more important than what we believe, and that social justice is the ideal toward which we strive.