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