The most comprehensive account of Paulician doctrine is within The Key of Truth, which was a Paulician text, written around 850 CE.

Paulicians believed that Jesus was the eternal, only-born Son. Jesus was a mediator of God and Man, but He was not a divine entity; Jesus was born and created a Man. Through Baptism, Jesus received the Holy Ghost and became Holy. Jesus was baptized on his thirtieth birthday.

The Paulicians recognized three sacraments as necessary for salvation: repentance, baptism and Eucharist. Repentance must be the first administered sacrament. Only after repentance could an individual be baptized. Infant baptisms were prohibited. Baptisms were to take place after an individual’s thirtieth birthday.

The Paulician religion consisted of a study of practical piety. Paulicians did not believe that churches were holier places than private homes for worship. The Paulicians greatly disapproved use of incense and consecrated oils in a religious manner. Strict iconoclasts, they also lobbied for the removal of any image of Christ or the Saints from churches. The Paulicians also looked upon the practice of penance as absurd.

The Paulician canon recognized the New Testament, except for the Apocalypse. The Paulicians also rejected the Logos doctrine, but the fourth gospel was accepted.