Q. 1. What is the heresy of "Monarchianism?"
A. 1. The heresy of "Monarchianism," started by Paul of Samosata, a bishop of Antioch, consist of a set of beliefs that emphasize God as being one person, in direct contrast to Trinitarianism which defines God as three persons coexisting consubstantially as one in being.
During the second century, different models of resolving the relationship between the God the Father and the God the Son were suggested. At a later time, these were rejected in favour of the doctrine of the Trinity as approved at the First Council of Constantinople. At that time, it was proclaimed that God was one being who consisted of three persons: the Father, the Son, and the Holy Spirit.