Congregations and resources in this category are Unitarian, Universalist, and/or Unitarian Universalist. Unitarianism historically developed from a critique of the Trinity as non-Biblical, and from a critique of the doctrine of original sin. In the 16th century belief in a unity of God (not a Trinity) and a single, human nature (not dual or divine nature) of Jesus led to the creation of Unitarian churches in Transylvania (Romania and Hungary) and in Poland. In the US and Great Britain the Unitarian Associations were both founded in 1825. Universalism is a religious faith incorporating many tenets of Christianity, but not exclusively Christian. It believes in universal salvation, or, as it is now generally stated, in the eternal progress of all souls. In the United States the Universalist movement was organized in 1793. The Unitarian Universalist Association (UUA) represents the interests of more than one thousand Unitarian Universalist congregations throughout North America. It was formed in 1961 by the merger of the Universalist Church of America and the American Unitarian Association.