What Every Catholic Needs To Know About The Early Heresies

by History of the Church

Anyone who wants to go deeper into their Christian faith will eventually come around to seeing the importance of the early Church, and those early Christian bishops, theologians, and catechists we call the Church fathers. When we say, “the early Church,” we’re talking about the time from the beginning, up until the 5th century – that is up until some time in the mid-to-late 400s. This is the primary time period that I am privileged to study and teach in my position as a Professor of Church History and Historical Theology. And you can’t study this important time period in the life of the Church without serious attention to those attempts at understanding the person of Jesus Christ and the Christian faith which turned out to be incorrect – those teachings and movements that we refer to as the heresies. And so here are a few things that every Catholic needs to know about heresies in the early Church.

Heresies In The Early Church

1) Heresy was often a well-meaning, but misguided, over-emphasis on one truth to the point of denying another important truth. For example, the heresy known as adoptionism (and its later version, Arianism) was a sincere attempt to protect monotheism. The adoptionists and Arians knew that there could be only one God, but they failed to understand the doctrine of the Trinity, and so they concluded that they could not believe in the divinity of Christ. They said, in effect, that God is one because Jesus is not God. And so they emphasized Jesus’ humanity to the point of denying his divinity.  Other heresies, called docetism and gnosticism, started with the idea that Jesus was divine, but then they could not see how the Divine could come to live a real human life, and so they refused to believe that “the Word became flesh,” and they emphasized his divinity, but denied his true humanity. 

2) The heresies forced the Church to clarify doctrine, especially by writing the Nicene Creed. By preaching incorrect interpretations of the Person of Christ, the heretics forced the early Church to clarify the true doctrines. In fact, we can already see this going on in the New Testament. For example, both Saints Paul and John confronted the heresy of early docetism in their letters. Defending the real humanity of Jesus, St. John wrote, “every spirit that acknowledges Jesus Christ come in the flesh belongs to God, and every spirit that does not acknowledge Jesus does not belong to God. This is the spirit of the antichrist…” (I John 4:2-3, emphasis mine). At the other extreme, when adoptionism evolved into the Arian heresy, the Church fathers responded by gathering in the first ecumenical (worldwide) council the Church, the Council of Nicaea, in the year AD 325. There, the first version of the Nicene Creed was written, which emphasized the divinity of Christ against the Arian heresy by affirming that Jesus Christ, the Son, is consubstantial with the Father (see my YouTube video on the meaning of “consubstantial”). Later, the Creed was finished at the second ecumenical Council of Constantinople in the year AD 381, when they added the clarifications on the Holy Spirit. The result of these corrections of heresy is our Nicene Creed, which is an authoritative summary of correct doctrine.

3) Heresy always has implications for salvation. If one is tempted to ask why it was such a big deal, and why the Church couldn’t just let everyone believe whatever they wanted to, the answer is that all heresy contradicts revealed truth, which is meant to lead us to salvation. In other words, all heresy leads people away from salvation because by teaching incorrect doctrine, people are encouraged to put their faith in a false god and a false christ. For example, if the adoptionists and Arians were right, and Jesus is human only, and not divine, then salvation is not by divine intervention, but rather by human effort. This is because, if Jesus Christ was a mere human, he first would have had to save himself through his own perfect obedience to God, and then the only way he could be a “savior” for us is by setting an example. We would then have to follow his example, and become perfectly obedient to God in order to save ourselves – but the Church fathers concluded that this would leave us hopeless. On the other extreme, if the docetics and gnostics were right, and Jesus Christ is divine only, but not human, then he might be able to be a Savior in some cosmic sense, but he could not save us, because he would not be one of us. Divine justice demands that the debt of sin that is owed by humanity, must be paid by humanity, and so it requires someone of human nature to pay for the sins of humanity. In other words, Jesus had to be one of us to represent us on the cross. Therefore our very salvation requires that Jesus Christ be both divine and human. Just one or the other will not do it.

4) Finally, there is nothing new under the sun. It’s important to understand that the early heresies never really went away. They were corrected, and they were dealt with, but they keep popping up again and again throughout history, and they still exist today. Adoptionism and Arianism, the heresies that diminish or deny the divinity of Jesus, are still around in the Jehovah’s Witnesses, Unitarian Universalists, Extreme Liberation Theology, and to a certain extent in the Mormons and Rastafarians. Docetism, and it’s later evolution gnosticism, are still around in Christian Science, the New Age movement & the occult (think crystals and tarot cards), Scientology, and to a certain extent in some aspects of Mormonism and in some Pentecostal groups. I’m not suggesting we all become heresy hunters, but we do need to be clear that correct doctrine matters, and it is not the case that all beliefs lead to salvation. 

Recommended Reading On Early Church Heresies

For more on all of this, read my book: 

Reading the Church Fathers: A History of the Early Church and the Development of Doctrine

And check out my YouTube series “The Original Church” at:



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