Messalianism is a heresy that originated in Mesopotamia about the year 360. The Messalians denied that the Sacraments gave grace, including baptism, and declared that the only spiritual power was constant prayer that led to possession by the Holy Spirit.
This heresy affected monasticism. Messalians were ascetics who practiced poverty, celibacy, and fasting. They rejected the sacramental life of the church and pretended to see God with their physical eyes. Their teachings spread into Syria and Asia Minor before the sect was finally anathematized by the Third Ecumenical Council of Ephesus in 431. Under the influence of the Messalians, the non-sleepers or Vigilant (Akoimetoi) type of monasticism developed in the area of Constantinople and was practiced even within the Studion Monastery, the monastery that became renowned for its polemic against the Iconoclasts.
Under Messalianism, intense meditation was supposed to achieve union with God and encourage the indwelling of the Holy Spirit, through which sinful inclinations would be purged and demons would be expelled. Such exaggerated claims included the ability to see demons and even the Holy Trinity. This clearly heterodox belief system, in many respects, had come more from Eastern mysticism than from the historic Christian faith. The obviously non-Christian content of the Messalianism made its condemnation at Ephesus uncontroversial. Due to their denial of the sacraments, the Messalians were almost entirely a lay movement. Thus, the clergy were universal in their denunciation of the heresy, a heresy that was punished with the usual canonical penalties.
- Commentary on the Council of Ephesus Definition against the Messalians
- Monasticism in the Orthodox Church