Unitarianism was rejected by orthodox Christianity at the First Council of Nicaea, an ecumenical council held in 325, but resurfaced subsequently in Church history, especially during the theological turmoils of the Protestant Reformation.
The Italian Anabaptist "Council of Venice" (1550) and the trial of Michael Servetus (1553) marked the clear emergence of markedly antitrinitarian Protestants.The Encyclopædia Britannica (11th edition) states: "to some Christians the doctrine of the Trinity appeared inconsistent with the unity of God. they therefore denied it, and accepted Jesus Christ, not as incarnate God, but as God's highest creature by whom all else was created. [this] view in the early Church long contended with the orthodox doctrine." Although the nontrinitarian view eventually disappeared in the early Church and the Trinitarian view became an orthodox doctrine of modern Christianity, variations of the nontrinitarian view are still held by a small number of Christian groups and denominations.Various views exist regarding the relationships between the Father, Son, and Holy Spirit.They also affirm that God is only explicitly identified as "one" in the Bible, and that the Trinity, literally meaning a set of three, ascribes a co-equal threeness to God that is not explicitly scriptural.Critics of the Trinity doctrine argue that it, for a teaching described as fundamental, lacks direct scriptural support.In America, Arian and Unitarian views were also found among some Millennialist and Adventist groups, though the Unitarian Church itself began to decline in numbers and influence after the 1870s.Nontrinitarian Christians with Arian or Semi-Arian views contend that the weight of scriptural evidence supports Subordinationism, that of the Son's total submission to the Father, and of paternal supremacy over the Son in every aspect.Theology · Early Christianity · Timeline · History of Christianity · Ecclesiastical polity · Trinitarianism · Nontrinitarianism · Restorationism · Christology · Mariology · Biblical canon · Deuterocanonical books Reformation · Luther · Melanchthon · Indulgences · Justification · Five solae · 95 Theses · Book of Concord · Predestination · Calvinism · Arminianism · English Reformation · Counter-Reformation · Trent Pietism · John Wesley · Great Awakenings · Holiness movement · Restoration Movement · Existentialism · Liberalism · Modernism in the Catholic Church · Postmodernism · Vatican II · Radical orthodoxy · Hermeneutics · Liberation theology · Christian anarchism Most nontrinitarians take the position that the doctrine of the earliest form of Christianity was nontrinitarian, but that early Christianity was either strictly Unitarian or Binitarian, or Modalist as in the case of the Montanists, Marcionites, and Christian Gnostics.For them, early Christianity eventually changed after the edicts of Emperor Constantine I and his sentence pronounced on Arius, which was later followed by the declaration by Emperor Theodosius I in the Edict of Thessalonica, cunctos populos of February 380 that Christianity as defined in the Nicene Creed was the official religion of the Roman Empire.His successors as Christian emperors promoted Arianism, until Theodosius I came to the throne in 379 and supported Nicene Christianity.The Easter letter that Athanasius issued in 367, when the Eastern Empire was ruled by the Arian Emperor Valens, specified the books that belong to the Old Testament and the New Testament, together with seven other books to be read "for instruction in the word of godliness"; it also excluded what Athanasius called apocryphal writings, falsely presented as ancient.