Q. 1. Can you summarize what was the heresy of adoptinism?
A. 1. The heresy of "Adoptinism" is also known as the heresy of "Psilanthropism" and "Dynamic Monarchianism."
This heresy promoted that Jesus was born of the Virgin Mary and the Holy Spirit as a human being (non-divine), that He was a very virtuous person and that He was adopted at a later date at baptism as the "Son of God" when the Holy Ghost descended on Him.
This belief was promoted in Rome in c.190 by Theodotus of Byzantium who was a leather merchant (also known as Theodotus the Tanner, Theodotus the Shoemaker, and Theodotus the Fuller.) At a later date, it was revived by Paul of Samosata who lived from 200 to 275 AD. Paul of Samosata was the Bishop of Antioch from 260 to 268 AD. He believed in monarchianism, a doctrine about the Trinity.
In 268 AD, Paul was condemned by the Synod of Antioch at which time time Theodotus was excommunicated by Pope Victor I.