Assyrian Church of the East
- Includes ancient and modern documents.
- http://www.nestorian.org

Heresies, Authority, Quarrels and Words
- An account and analysis of belief systems declared heretical by the Catholic Church. Site is sharply critical of authority and religion, and especially of the Church.
- http://www.abelard.org/heresies/heresies.htm

Marcionites [Catholic Encyclopedia]
- Said that the creator "god" of the Old Testament was not the good God and Father of Jesus Christ of the New Testament. Had their own shadow hierarchy and their own Bible, which consisted of parts of Luke and Paul, edited so as to disparage the O
- http://www.newadvent.org/cathen/09645c.htm

Monarchians [Catholic Encyclopedia]
- The so-called Dynamic Monarchians were actually a form of adoptionism. Monarchianism, properly speaking, refers to the Modalists. Denial of the Trinity, assertion that there is only one Divine Person, who appears in three different roles. Noetians and Sa
- http://www.newadvent.org/cathen/10448a.htm

Ebionites [Catholic Encyclopedia]
- Two varieties: the earlier group called Ebionites denied the divinity of Christ; the later Ebionites were a Gnostic sect who believed that matter was eternal and was God's body.
- http://www.newadvent.org/cathen/05242c.htm

Monophysites and Monophysitism [Catholic Encyclopedia]
- Rejected the dual nature of Christ. Rejected by the Council of Chalcedon (451).
- http://www.newadvent.org/cathen/10489b.htm

Pelagianism [Catholic Encyclopedia]
- Belief founded by Pelagius that denied original sin as well as Christian grace. Rejected by the Council of Carthage (481)
- http://www.newadvent.org/cathen/11604a.htm

Nestorianism [Catholic Encyclopedia]
- Belief attributed to Nestorius that Christ's two natures reflect two persons, and denying of the Virgin Birth. Rejected by the Council of Ephesus (431).
- http://www.newadvent.org/cathen/10755a.htm

Docetae [Catholic Encyclopedia]
- Docetism, from the Greek "dokeo" (to seem, to appear) was the contention that Christ merely seemed to be human and only appeared to be born, to suffer, and to die. Already in New Testament times, the Gospel of John opposes Docetism, and so do Ig
- http://www.newadvent.org/cathen/05070c.htm

Adoptionism [Catholic Encyclopedia]
- The theory that the man Jesus at some point in time became the Son of God only by adoption. Strictly speaking, refers to an eighth-century Spanish heresy, but the term is also used to cover similar beliefs.
- http://www.newadvent.org/cathen/01150a.htm

Arianism [Catholic Encyclopedia]
- Founded by Arius, belief asserting that Christ was not God like the Father, but a creature made in time. Rejected by the Council of Constantinople (381).
- http://www.newadvent.org/cathen/01707c.htm

Monothelitism and Monothelites
- A modification of Monophysitism proposing that Christ had no human free will. Rejected by the Third Council of Constantinople (680).
- http://www.newadvent.org/cathen/10502a.htm

Apollinarianism [Catholic Encyclopedia]
- Fourth-century Christological heresy propounded by Apollinaris of Laodicea. The theory that Jesus had a human body and soul, but that the Logos took the place of the human spirit or mind in Jesus. Solemnly condemned at the Council of Constantinople in 381
- http://www.newadvent.org/cathen/01615b.htm