Pelagianism: History, Definition, & Beliefs (Heresy Series)

Disclaimer: The views and opinions expressed in this article belong to the author and do not necessarily match my own. - Dr. Bart D. Ehrman

“Excuse me, Professor! Can you tell me what Pelagianism is?” I must admit, that’s a question I rarely (if ever) hear in my classroom. 

Most of my students, even those who love early Christian history and are eager to learn more about it, have never encountered the term. It’s not a word that rolls easily off the tongue, and it certainly doesn’t enjoy the name recognition of movements like Gnosticism or Arianism. 

Yet its story is no less fascinating, and its impact on the development of Western Christianity has been profound.

That's a shame, because beneath that obscure label lies a series of polemics and debates that helped define what it meant to be Christian in the Latin-speaking world of late antiquity. The issues at stake weren’t abstract puzzles for theologians alone.

They touched on how ordinary believers understood sin, human freedom, and the very possibility of salvation. To trace the contours of this ancient controversy is to see the early church wrestling with questions that still resonate: Are human beings truly free to choose good over evil? Do we need divine grace to live rightly? What does it mean to say that humanity is “fallen?”

The struggle over these questions, of course, didn’t arise in a vacuum. By the time this debate erupted in the early 5th century, Christianity had already weathered generations of fierce disagreement.

It was in this world of moral rigor and theological tension that a British monk arrived on the scene, challenging assumptions that many thought were beyond dispute. His teachings would provoke one of the most consequential debates in Christian history.

Join me as we enter together in the world of early Christian heresies to reveal what is hidden beneath the word “Pelagianism.” To do that, we must, first and foremost, take a brief look at the major features of the Christian world in the 3rd and 4th centuries.

Pelagianism and the Historical Context: Debates and Struggles

From its very beginning, Christianity wasn’t a monolithic movement, but a remarkably diverse phenomenon. Already by the 2nd century, there existed a wide variety of Christian communities scattered throughout the Roman Empire, each holding different and often opposing views on some of the most fundamental questions of faith.

How was the world created? Who exactly was Jesus? Was he divine, human, or somehow both? How could humans be saved, and what was their role in the process? On each of these issues, opinions diverged sharply.

One well-known group, the Marcionites, for example, followed the teachings of Marcion of Sinope, who rejected the Jewish Scriptures altogether and claimed that the harsh Creator God of the Old Testament was distinct from the loving Father proclaimed by Jesus.

In contrast, the movement that modern scholars often call “proto-orthodoxy” (the strand of Christianity that would later become dominant) affirmed the continuity between the Hebrew Bible and the Christian message. They insisted that the God of Israel and the Father of Jesus were one and the same.

If you really want to get into the diverse world of early Christianity (the movements, debates, and “heretical” voices that shaped the faith’s first centuries) don’t miss Bart Ehrman’s 8-lesson course, Earliest Christian Heresies. 

In it, Bart brings to life the forgotten teachers, rival gospels, and theological battles that defined the boundaries of belief. You’ll encounter not just the winners of history, but the fascinating diversity of ideas that once thrived across the ancient Christian world.

Each of these communities, however, believed that it alone represented the true faith of Jesus and his apostles. This conviction naturally led to tensions, polemics, and sometimes (after Constantine converted) outright persecution.

But, the central strategy was often rhetorical rather than physical: to delegitimize one’s opponents by denying that they were “real” Christians at all. As M. David Litwa explains in his book Found Christianities:

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Even within this web of internal diversity, certain regional characteristics began to emerge. As it turns out, one can trace two distinct trajectories in the development of Christian thought, depending on geography.

In the Greek-speaking East, theological battles were largely Christological, concerned with the identity and nature of Christ and his relationship to God the Father. Was Jesus subordinate to God, equal to him, or one with him in essence?

The 4th-century conflict over Arianism, which denied the full divinity of Christ, epitomizes this focus. (Readers interested in this equally fascinating debate can find a dedicated article on Arianism in this same series.)

By contrast, the controversies that shaped Western Christianities (and I deliberately use the plural here, because, as a historian, I recognize that all these competing branches and communities were genuinely Christian, regardless of the “proto-orthodox” claims to exclusivity) tended to revolve around issues of discipline, morality, and salvation. 

In other words, the West was less preoccupied with defining the metaphysical nature of Christ than with determining how believers ought to live, how the Church should handle sin, and who truly belonged to the community of the saved. 

The fierce conflict known as Donatism, for instance, arose in North Africa over whether priests who had lapsed under persecution could administer valid sacraments. (Perhaps we’ll devote a future article to that movement as well!)

It was within this western landscape (where questions of moral rigor, repentance, and grace loomed large) that another major controversy would soon erupt: Pelagianism. Emerging in the early 5th century, it reignited the old debate over human freedom and divine assistance.

To understand what Pelagianism actually taught and how the Church responded, we must now turn to its origins, definition, and central ideas, but this time, viewed through the careful lens of critical historiography, not merely through the polemics of its opponents or the verdicts of those who ultimately triumphed.

What Was Pelagianism? Definition, Origins, and Aftermath

The term Pelagianism (definition: the belief that human beings can choose good without the necessity of divine grace) takes its name from Pelagius, a real historical figure. He was a British monk, theologian, and moral teacher active in the late 4th and early 5th centuries. 

Little is known about his early life, though most sources agree he was born in Britain sometime in the second half of the 4th century and received a solid education in Scripture and classical learning.

By the 380s or 390s, he had made his way to Rome, where his ascetic discipline and moral seriousness attracted a circle of admirers among the city’s Christian elite. 

To many Roman Christians, Pelagius appeared as a model of integrity in an age of moral laxity. The empire was in crisis, and the Christian Church, now officially established, had begun to mirror the ease and privilege of the aristocracy. 

It was within this turbulent and uncertain world that Pelagius’ public career began to unfold; a world shaken by political instability, moral decline, and profound religious transition.

As Georges de Plinval explains in his classic study Pélage: ses écrits, sa vie et sa réforme (Pelagius: His Writings, Life, and Reform):

To put it more bluntly, the Rome that Pelagius entered was a city torn between its pagan heritage and its Christian destiny; a world hungry for moral clarity and ripe for the kind of reforming voice he would soon embody.

Pelagius’ response wasn’t theological or philosophical speculation but moral exhortation: a call to live as authentic Christians through virtue, effort, and commitment.

When Alaric’s sack of Rome in 410 C.E. drove many from the city, Pelagius departed as well: first to North Africa, then to Palestine. Along the way, he came into contact with Augustine of Hippo, already one of the most formidable theological minds of the age. 

The two never engaged in direct (in-person) debate, but Augustine would become Pelagius’ fiercest opponent. From Augustine’s perspective, Pelagius’ teachings undermined the very foundations of Christian religion.

But what did Pelagius teach that was so dangerous for the emerging orthodoxy? Why was he considered a heretic?

To understand this, we must look at two very different interpretations of his thought. The first is the traditional paradigm, represented by Augustine and those who followed in his footsteps. The second is a more nuanced modern interpretation, grounded in close analysis of Pelagius’ surviving writings and free from any theological agenda.

Pelagianism: Beliefs of Pelagius According to the Traditional Paradigm

According to the Church’s traditional narrative (formulated largely by Augustine and preserved through centuries of theological teaching), Pelagianism heresy denied the necessity of divine grace. 

In Augustine’s retelling, the troublemaker from Britain taught that human beings, by their own free will and natural capacity, could fulfill God’s commandments and achieve moral perfection. Adam’s sin, in this view, harmed only himself; it didn’t corrupt human nature or transmit any inherited guilt. 

Each person, Pelagius allegedly maintained, is born innocent, as Adam was before the Fall. Grace, therefore, was merely a form of divine assistance (moral instruction or encouragement) rather than the transformative power that rescues humanity from sin.

In this interpretation, Pelagius’ theology amounted to a radical self-sufficiency of the human will. If salvation could be attained by human effort, Augustine argued, then Jesus’ sacrifice was rendered superfluous. 

The moral optimism of Pelagius, far from inspiring holiness, seemed to Augustine a dangerous illusion. For him, it was only a new version of the ancient pride that had led Adam to his fall in the first place.

“Without me you can do nothing,” Jesus says in the Gospel of John, and Augustine saw in Pelagius’ moral confidence a subtle defiance of that divine warning.

In the words of Augustine (Book II; Chapter 18) himself:

From this perspective, Pelagianism threatened to undo the entire Christian understanding of grace, redemption, and dependence on God. It also posed pastoral dangers. If people believed that salvation could be earned by their own strength, Augustine warned, they would either fall into arrogance or despair.

Grace, for him, wasn’t optional assistance but the very condition of human goodness. Pelagius’ denial of original sin and his faith in human freedom became, in the eyes of the Church, the seeds of heresy.

It comes as no surprise that local councils at Carthage (418 C.E.) and later Ephesus (431 C.E.) condemned the movement outright, declaring that salvation comes through grace and that even the desire to do good originates in God’s initiative, not human effort.

Pelagianism From the Modern (Scholarly) Perspective

Modern scholarship, however, has significantly complicated this picture. Brinley R. Rees, in his study Pelagius: A Reluctant Heretic, portrays Pelagius not as a defiant theologian intent on dismantling orthodoxy, but as a sincere moral reformer deeply disturbed by the spiritual complacency of his time.

Far from denying grace, Pelagius sought to remind Christians of their moral responsibility. His genuine Pelagianism beliefs, as seen in his letters and commentaries, centered on moral effort supported by divine help rather than its rejection. Through baptism, believers are cleansed from past sins and empowered to live uprightly.

Pelagius’ focus was ethical rather than metaphysical! He wanted Christians to act as if they truly had been transformed by grace. For Pelagius, the command “Be perfect, as your heavenly Father is perfect” wasn’t an impossible ideal, but an earnest moral summons.

Ali Bonner, in her book The Myth of Pelagianism, goes even further, arguing that the entire construct of “Pelagian heresy” was largely a literary creation of its opponents. The famous list of “Pelagian doctrines” attributed to him (denial of original sin, rejection of baptismal grace, exaltation of human will) cannot be found in Pelagius’ extant writings.

On the contrary, he repeatedly speaks of divine help, the aid of the Holy Spirit, and the cleansing power of Christ’s blood. He never taught that humans could attain sinless perfection on their own, nor that baptism was unnecessary for infants.

Much of what later became “Pelagianism,” Bonner demonstrates, originated not with Pelagius but with others, particularly his associate Celestius, and was then attributed to him by Augustine in the heat of controversy.

Furthermore, Winrich A. Löhr’s meticulous reconstruction of Pelagius’ lost treatise De natura (preserved only through Augustine’s quotations in De natura et gratia) demonstrates that Pelagius didn’t deny grace but defined it differently. 

When his interlocutors in De natura insist that moral perfection is possible “only by grace,” Pelagius readily agrees, but interprets this to mean that God’s grace operates through the very faculties God created: reason, will, and the moral law.

Augustine read this as reducing grace to mere “nature and teaching,” but Pelagius seems instead to have been preserving a synergistic model in which divine empowerment and human freedom cooperate.

Where Augustine saw grace as an unmerited, irresistible gift preceding any human act, Pelagius saw it as God’s continual empowerment, the daily assistance enabling humans to choose rightly. 

Put simply, Pelagius’ theology was synergistic rather than monergistic. He believed that grace and human effort cooperate in salvation, instead of salvation being accomplished by God alone. His central concern was moral fairness: if God commands it, humans must be capable of responding. Otherwise, divine justice would make no sense.

The heart of the conflict, therefore, wasn’t arrogance versus humility but two distinct ways of understanding divine-human cooperation. 

Augustine, haunted by his own experience of inner struggle, stressed humanity’s helplessness apart from God’s intervention. 

Pelagius, formed in the ascetic culture of Rome, stressed responsibility, self-discipline, and the potential of grace to transform moral character. These weren’t two different religions, but two different temperaments within the same religious tradition.

In retrospect, the so-called Pelagian heresy looks less like a coherent movement and more like a rhetorical construct — a boundary line drawn by Augustine and his allies to define emerging orthodoxy. 

As Bonner argues, the label “Pelagianism” functioned as a kind of theological shorthand for everything Augustine rejected: confidence in human freedom, moral rigor, and any hint of synergy between divine and human will.

Consequently, Rebeca Lyman, confirms the communis opinio:

Unfortunately, behind this caricature, a real (historical) Pelagius disappeared. A man sincerely devoted to moral renewal, condemned not so much for what he said as for what others thought he implied. 

Whether one accepts the traditional Augustinian narrative or the more nuanced view emerging from modern scholarship, the fact remains that Pelagianism (real or constructed) suffered a particular fate. 

The moral reformer became the heretic; the call to responsible holiness became a warning against pride. What began as a debate over human freedom and divine grace would echo through medieval theology, the Reformation, and even beyond.

But what happened to Pelagius himself, and how did the Church finally deal with this controversy? To answer that, we must turn to the next section of our story, one that traces the fate of the man and the movement that bore his name.

But before we do that, take a moment to look at the table below. It neatly encapsulates the key differences between Pelagius as portrayed by Augustine and Pelagius as understood by modern scholarship.

Think of it as your intellectual “cheat sheet”. It’s a kind of table that can save you from theological embarrassment at a dinner party or a conference Q&A. It distills a century of polemic and decades of scholarship into one elegant snapshot (yes, we are that good!).

Pelagianism After Pelagius

The polemical battle between Pelagius and Augustine soon spilled over the top of the Church’s hierarchy, followed by a serious read-through at several local synods. The first decisive turn came after Diospolis (Lydda, 415), where Pelagius (without his accusers present) professed the necessity of “God’s help” and was acquitted by Palestinian bishops

Augustine read the minutes and judged the acquittal crafty: Pelagius, he argued, had equivocated on what “grace” truly meant. 

African bishops responded with a sequence of synods (Numidia and Proconsular Africa) and set the stage for a general council at Carthage on May 1, 418 C.E., which issued eight or nine canons against alleged Pelagian propositions.

In his book The Early Church, Henry Chadwick argues that this African push was the moment when the controversy ceased to be a private quarrel and became a public test of doctrine, with the canons effectively codifying the Augustinian reading of sin and grace.

In Rome, the papal stance briefly wavered. Pope Zosimus (417-418 C.E.) initially found Pelagius and his disciple Celestius persuasive and rebuked the Africans for acting precipitately. But North African bishops doubled down, and a decisive imperial rescript from Honorius (30 April 418 C.E.) expelled Pelagians from Rome as a threat to public order.

Under imperial pressure, Zosimus reversed course in 418 C.E. and circulated the Epistola tractoria (a letter sent to bishops across the West), requiring subscription to anti-Pelagian positions and sealing the condemnation. 

Chadwick highlights both the ecclesiastical and political vectors at work here: episcopal lobbying, imperial concerns over social stability, and Rome’s eventual alignment with the African synods’ theological judgement.

What of Pelagius himself? After the Diospolis acquittal, he remained in the East; sources place him in Palestine through 418 C.E., corresponding with aristocratic patrons, and then he disappeared from the record, likely dying somewhere in the Orient.

His associate Celestius continued to press the cause (even appealing to Rome), but the network around Augustine out-maneuvered him diplomatically; by 418 both men stood condemned in the West. 

Chadwick notes that Pelagius’ last public statements kept returning to a single point: that a good work requires God’s help but also entails a genuinely free human act. That was precisely the formulation Augustine judged inadequate because it reduced grace to external aid rather than interior transformation.

The wider Church then “internationalized” the African line. 

While the Council of Ephesus (431 C.E.) is remembered chiefly for its Christological decisions against Nestorius, the acts and accompanying dossiers also confirmed the condemnation of Pelagius and Celestius.

Later canonical collections (via Trullo’s reception of African canons) reinforced this posture. In short: by the mid-5th century, “Pelagianism” stood officially proscribed in both local African and ecumenical registers.

However, condemnation didn’t end debate; it redirected it. 

In southern Gaul, monastic circles around John Cassian and Vincent of Lérins proposed a mediating account (often dubbed “semi-Pelagian” by later writers), insisting that grace is prior and necessary but that the first stirrings of faith and the ongoing Christian life involve real cooperation of the will. 

After a century of tug-of-war (including interventions by Prosper of Aquitaine), the Council of Orange (529 C.E.) offered a durable settlement: grace truly precedes and enables every beginning of faith, yet the baptized, aided by Christ, bear responsibility to “labor faithfully.”

In other words, this council rejected Pelagian and hard determinist extremes alike; later Western theology would repeatedly revisit its balance, and the rest became history!

Conclusion

So, if a student were to raise that rare question (“Excuse me, Professor, what exactly is Pelagianism?”), we might now answer it not with a slogan about “works versus grace,” but with a story about how early Christians tried to understand the mystery of human freedom in the light of divine mercy.

Behind the label lies a centuries-long polemic over moral effort, dependence, and responsibility, a debate that began with one British monk’s plea for integrity and ended by helping to define the contours of Western theology itself.

The controversy surrounding Pelagius reminds us that the history of doctrine is rarely a simple tale of right and wrong ideas. It is, rather, the record of how believers in different circumstances sought to express the balance between God’s initiative and human response.

Perhaps the real legacy of Pelagianism, stripped of its polemical baggage, is that it still invites us to reflect (historically, ethically, and even theologically) on what it means to be responsible, and what it means to be redeemed.

Appendix: Does the Bible Mention Pelagianism?

This question gets us right into the realm of biblical exegesis, but one that must remain attentive to historical and literary context, without projecting later theological developments onto the biblical text. The term Pelagianism is, of course, post-biblical.

Still, the debate between Pelagius and Augustine wasn’t invented in a vacuum. Rather, both thinkers appealed constantly to Scripture, each claiming fidelity to the Christian tradition.

Passages emphasizing human responsibility and moral choice were central to Pelagius’ reading of the Bible. He cited texts such as Deuteronomy 30:19 (“I have set before you life and death, blessings and curses. Choose life”), and Matthew 5:48 (“Be perfect, therefore, as your heavenly Father is perfect.”)

Augustine, however, appealed to another set of texts: Romans 5:12-21 on the transmission of Adam’s sin, and Ephesians 2:8-9 on salvation as “the gift of God, not the result of works.” For him, these verses proved the primacy of divine initiative and the radical dependence of the human will on grace.

I’d say that the Bible itself contains no explicit doctrine of “Pelagianism” or “anti-Pelagianism.” What it offers are diverse voices that later theologians interpreted through different lenses. The controversy of the 5th century thus reflects the tension already present within Scripture between divine sovereignty and human responsibility.