When it comes to reading the Bible, many Christians often assume the passages are clear and conspicuous enough to be self-interpreting. Yet time after time, we are proven that Scripture requires a second set of eyes. At the same time, we are continuously warned about the existence of false teachers and how easily they sneak potentially  into Church doctrine, pastoral sermons or even your weekly Bible study. And as time passes by, old heresies once condemned by generations long gone resurrect themselves years or centuries later. There truly isn’t anything new under the sun, it just resurfaces wearing a different mask.

While there are dozens of heresies defined by the Church throughout history, I’ve gathered and compiled a list of 12 of the most common theological errors found in Christian culture, along with links to their respective articles in Catholic Answers.

Montanism

Montanism is a prophetic movement that originated in Phrygia, a province of Asia Minor. It spread rapidly throughout the Roman Empire before Christianity was legalized by Constantine in the 4th century A.D., and flourished well into the 6th century. It seemingly withheld the basic tenets of Christian doctrine to those of the universal Christian Church, but due to its strong promotion of new and ongoing prophetic revelation, it was labelled a heresy.

The prophetic movement placed heavy emphasis on the spontaneous move of the Holy Spirit and a more legalistic personal morality. Some have drawn parallels between Montanism and modern charismatic revival movements associated with Pentecostalism and other charismatic assemblies.

Tritheism

Tritheism is a belief which emphasized the individuality of each person of the Trinity (the Father, the Son and the Holy Spirit) over the unity of the Trinity as a whole. Various theologians throughout Church history have been accused of tritheism, especially between the 3rd and 7th centuries A.D. Some theologians taught the nature of the Trinity is a form of abstraction — meaning while the Father, the Son and the Holy Spirit are consubstantial they are distinct in their autonomy. This view was condemned as heresy at the Third Council of Constantinople in the 7th century.

Jews, Muslims, Jehovah’s Witnesses, Mormons and certain Evangelical Protestants have often accused those who believe in the Trinity as polytheists disguised as Christians.

Docetism

Docetism is the ideology that Jesus’s historical and bodily existence (namely the human form of Jesus) was merely a semblance without any basis in reality. It generally believes that Jesus’s humanity was an illusion.

The Greek word Δοκηταί (Dokētaí) means ‘Illusionists,’ which refers to some early groups who denied Jesus’s humanity. Bishop Serapion of Antioch was the first to propagate the ideology after he discovered it mentioned in the apocryphal Gospel of Peter in the latter of the second century, but later condemned the text as a forgery. Some believe it arose over theological contentions concerning a passage regarding how ‘the Word was made Flesh (John 1:14).’

Docetism was debated and rejected at the First Council of Nicaea (325 A.D.) and is unanimously deemed heretical by the Catholic Church, Eastern Orthodox Church and many Protestant denominations that adhere to the statements of the Early Church councils.

Arianism

The word ‘Arian’ is derived from the name Arius who was a Christian presbyter in Alexandria, Egypt from the third to fourth century. Arianism asserts that Jesus (as the Son of God) did not always exist, but was begotten by God the Father at a specific point in time. This would render Jesus to be a created creature distinct from and subordinate to the Father while still being considered God the Son.

The First Council of Nicaea in 325, which was summoned by Emperor Constantine to ensure Church unity, debated and concluded Arianism to be a heresy. Arianism is a term that is also loosely utilized to refer to other non-trinitarian theological systems which regard Jesus as a begotten creature, or as neither created nor uncreated (the former referred to as Semi-Arianism).

In the present day, the Church of Jesus Christ of Latter-Day Saints and the Kingdom Hall of Jehovah’s Witnesses are often critiqued by most Christians that they view Jesus in the same manner as the Arians of the fourth century.

Nestorianism

Nestorianism is attributed to a Christian theologian named Nestorius, who was the Patriarch of Constantinople from 428 to 431. It emphasizes that the human and divine natures of Jesus Christ were joined by will rather than by personhood.

Nestorius’ teachings were heavily criticized by church leaders (most notably Cyril of Alexandria), who criticized his rejection of the Virgin Mary’s title of Theotokos (Greek for ‘God-bearer,’ which also translates as ‘Mother of God’). Nestorius and his teachings were eventually condemned at the Council of Ephesus in 431, and again at the Council of Chalcedon in 451. This led to the Nestorian Schism, in which churches that supported Nestorian teachings broke off from the rest of the universal Christian Church.

Many non-denominational Christians who claim that Mary is strictly the mother of Jesus and not God unknowingly commit the heresy of Nestorianism. Logically, it minimizes the divinity of Christ and belittles the role of Mary as the Mother of God.

Monophysitism

Monophysitism is the belief that Jesus Christ had only one single ‘nature’ which was either divine or a hybrid of divine and human. It is contrasted to duophysitism, which asserts that Christ maintained two natures (one divine and one human) after the incarnation.

After the Council of Chalcedon in 451, the controversy over monophysitism led to the Oriental Orthodox churches to break off in schism. The vast majority of Christians (namely the Eastern Orthodox, Roman Catholic and traditional Protestant churches who accept at least the first four Ecumenical Councils) have always claimed monophysitism is a heresy due to how it implies Christ is neither ‘true God’ nor ‘true man.’

Modalism

Modalism (also known as Sabellianism) is the belief that the Father, Son, and Holy Spirit are three different modes or aspects of God, rather than three distinct persons within the Trinity. It has been generally believed to have gained popularity in the second and third centuries, and has been rejected by the majority of the universal Church in favor of describing the Godhead as three distinct, co-equal, co-eternal persons of one substance by the Athanasian Creed.

Athanasius of Alexandria (who was responsible for the Athanasian Creed in the 5th century) used the Greek term homoousian (ὁμοούσιος) which meant ‘same being’ or ‘consubstantial.’ This was to affirm the Father and Son are eternally distinct in a truly personal manner, while still one being, nature, essence or substance. Sabellius (whom Sabellianism is named after), on the other hand, considered the Father and the Son to be ‘one substance,’ though operating as different manifestations or modes.

Many Christians, regardless of denomination, often use the different states of water as an example of explaining the Trinity. Because water can either take the form of solid ice, liquid or a vaporous gas, this often paralleled with the relationship between the Father, the Son, and the Holy Spirit. However,

Pelagianism

Pelagianism is the belief that Original Sin did not taint human nature and that the human will is freely capable of choosing good or evil without any divine assistance. This theological concept is coined after a fourth-century monk named Pelagius who taught human free will is sufficient to live a sinless life. Pelagianism (whether taught by Pelagius himself or not) has been summarized with the view that human beings are capable of earning salvation by their own efforts. In his opinion, the inherent value of Christ’s redemption was mainly limited to example and instruction.

Although many Reformed Christians have accused Catholics and Orthodox of sneaking Pelagianism in their teachings regarding penance and good works, both Pelagianism and Semi-pelagianism have been condemned at the Council of Orange in 529 A.D. whose authority is acknowledged by both the Catholic and Eastern Orthodox Churches.

Donatism

Named after the bishop Donatus Magnus, Donatism is the theological position that Christian clergy must be completely faultless in order for their evangelism to be effective and their prayers and sacraments to be valid. It was a heresy that led to a schism in the Church of Carthage spanning from the fourth to sixth century A.D. Donatism had spread in the wake of persecution of Christians under Diocletian in the Christian communities of what is now Tunisia and Algeria.

Some Catholic apologists have argued that radical traditionalist movements such as sedevacantism (the idea that all Popes after Pius XII as well as the Novus Ordo Mass are invalid) is a form of Donatism.

Gnosticism

Gnosticism comes from the Greek word γνωστικός (gnōstikós), meaning ‘having knowledge.’ It is a collection of ancient religious ideologies and practices originating from the first century A.D. among early Christian and Jewish sects who were labeled ‘gnostics’ by their opponents. These groups emphasized the acquisition of gnosis (personal spiritual knowledge) which took primacy over Gospel teachings, traditions, and ecclesiastical authority. They believed the element of salvation to be direct knowledge from a higher divinity, experienced as intuitive or esoteric insight. Gnosticism generally presents a distinction between spiritual transcendence and being blinded by the material universe which is believed to be an obstacle to a higher consciousness. Gnosticism often avoids the concepts of sin and repentance, but rather promotes enlightenment through unveiling ‘secret knowledge.’

Gnosticism is probably one of the most common heresies in all of Christendom. Some theologians have observed that the New Age Movement, which bears significant influence throughout Western civilization, is a modern-day form of Gnosticism.

Dualism

Dualism is the idea of two deities or deistic principles, one good and the other evil. This was the basis of a Gnostic revival movement known as Catharism. The Cathars thrived in portions of Southern Europe between the 12th and 14th centuries, namely what is present-day southern France and northern Italy. They believed the good God was the God of the New Testament who was creator of the spiritual realm, whereas the God of the Old Testament was the evil creator of the physical world whom they considered to be Satan. They also believed human souls were actually sexless spirits of angels trapped in the material realm like ghosts in shells by the evil god. They were supposedly destined to be reincarnated until they achieved a status of perfection through the Consolamentum ritual, by which Cathar individuals were consecrated and raised to return to the good god.

Dualism (especially Catharism) directly contrasts the Christian principle that there is only one God, the same God who exists in the Old and New Testament, who created all things visible and invisible.

Jansenism

Like Calvinism (a Protestant theological movement), Jansenism places significant emphasis on Original Sin, human depravity, the necessity of divine grace and predestination of souls. The written works of late Dutch theologian Cornelius Jansen were popularized by his friend Abbot Jean du Vergier de Hauranne well after his death in 1643. Jansenism was known to be a distinct departure away from Catholicism through the 17th and 18th centuries.

Although Jansenists identified as adherents to the teachings of Saint Augustine, the movement was vehemently condemned by many within the Catholic hierarchy, especially the Jesuits who coined identified them as having Calvinist affinities. In response, the Jansenists accused the Jesuits for contradicting the teachings of Augustine regarding the relationship between human free will and efficacious grace. In 1653, Pope Innocent X condemned five tenets of Jansenism as heretical in his papal exhortation Cum Occasione.

While the Jansenists moved to accommodate the Pope’s demands, they managed to retain their uniqueness and enjoyed relative peace under the authority of Pope Clement IX. However, increasing tensions led Pope Clement XI to release the apostolic constitution Unigenitus Dei Filius in the early 18th century.

Other recommended reading if you’re wanting to dig deeper:
https://www.catholicculture.org/culture/library/view.cfm?recnum=7012