Adoptionism is a form of the heresy of Monarchianism that appeared in varying forms in the second and third centuries and then again in the eighth and twelfth centuries in the West. The Christological view held was that Jesus was born human and became divine later during his baptism and thus was adopted as the son of God. This form of the heresy differs from Modalism, the other form of Monarchianism, in which the “Father” and the “Son” are two aspects of the same subject. The adoptionism heresy revived again in the West during the eighth century by the bishops of Toledo and Urgell. It again appeared during the twelfth century in France as Neo-Adoptionism.
The adoptionistic idea may have had its origin within the first century after Christ, and according to one theory, the oldest extant work that expressed the idea, Shepherd of Hermas, appeared in the second century. According to one interpretation of this work, the Redeemer, Jesus, was thought to be a virtuous man, chosen by God, who was united with the Spirit of God and did works as God commanded. Jesus, thus, was adopted as Son by divine decree. This then denied the preexistence of Christ. In this form the heresy continued during the second and third centuries. However, some theologians like the Orthodox professor Bogdan Bucur believe that it is not Adoptionist and take the view that in the Shepherd, the "holy, pre-existent Spirit" that created the world and that God made to dwell in the flesh is Christ's own personal Spirit, not the Third Person of the Trinity (called "The Holy Spirit" in the Nicene Creed). Under this second theory, this concept of Christ's "Spirit" is reflected in John 1:14 ("And the Word became flesh and dwelt among us") and in 1 Peter 1:10,11 and I Cor. 3, wherein Christ's Spirit dwelt in the prophets and dwells in believers, respectively.
Known also as Dynamic Monarchianism, an early proponent of the heresy was Theodotus (the Tanner) of Byzantium. He taught, after arriving in Rome about 190, that the man Jesus was born of the virgin through the operation of the Holy Spirit and after the Holy Spirit descended upon him at his baptism, he became Christ and received the power for his ministry and then became God through his resurrection.
Condemned early as a heresy this adoptionist view entered into the ideas of a number of later heretical positions, such as those by Paul of Samosata, Arius, Nestorius, and others during the Christological arguments of the next several centuries.
Adoptionism appeared again during the eighth century on the Iberian peninsula and again in the twelfth century in France. The adoptionist heresy was revived by Elipandus, the Archbishop of Toledo, in Spain late in the eighth century in the isolated atmosphere of Mohammedan rule and in an area where a Nestorian colony had found refuge. In defending his position, Elipandus received aid from Felix, the bishop of Urgell in the Pyrenees, who taught a similar position. It was only after great efforts were made that the erring people returned to orthodoxy. While Elipandus was not removed as archbishop of Toledo, the adoptionist heresy was almost universally abandoned after his death.
In the twelfth century, Peter Abelard, in France, preached a variation of the heresy called Neo-adoptionism that, along with later variations, was based on erroneous understandings of the hypostatical union.