Arianism and Pelagianism: Two Great Heresies of the Fourth and Fifth Centuries

At a time in Western civilization when differing religious theologies were at odds with each another, opposing schools of thought attempted to reformulate and rationalize some the most fundamental teachings heart early Christianity. As founders these branded as radicals heretics for defying orthodoxy authority Roman Empire same time, Catholic Church, teachers soon ostracized harshly punished their flawed erroneous beliefs. Focusing on fourth fifth centuries Common Era specifically, this paper will introduce two great heresies that belonged those historical periods namely, Arianism Pelagianism, highly influential, yet controversial thinkers behind them. Formulated by Cyrenaic (modern-day Libya) presbyter, Arius (256-336 CE) British monk theologian, Pelagius (390-418 CE), figures whose nonconformist theological positions are still being debated today, dared own defiant ways challenge firmly established rules doctrines Crown Church.