Heresy, according to the Oxford English Dictionary, is a "theological or religious opinion or doctrine maintained in opposition, or held to be contrary, to the ‘catholic’ or orthodox doctrine of the Christian Church..."
The word "heresy" comes from the Greek αἵρεσις, hairesis (from αιρεομαι, haireomai, "choose"), which means either a choice of beliefs or a faction of dissident believers. It was given wide currency by Irenaeus of Lyons in his tract The Detection and Refutation of False Knowledge (commonly known by the title of the Latin translation, Contra Haereses (Against Heresies) to describe and discredit his opponents in the early Christian Church. He described his own position as orthodox (from ortho- "right" + doxa "glory" or "belief").
Early Christian heresies
Urgent concerns with the uniformity of belief and practice have characterized Christianity from the outset. The process of establishing orthodox Christianity was in full swing by middle to late first century when Paul wrote the epistles that comprise a large part of the New Testament. On many occasions in Paul's epistles, he defends his own apostleship, and urges Christians in various places to beware of false teachers, or of anything contrary to what was handed to them by him. The epistles of John and Jude also warn of false teachers, as does the writer of the Book of Revelation.
During the first three centuries, Christianity was effectively outlawed by requirements to worship the Roman emperor and Roman gods. Consequently, when the Church labeled its enemies as heretics and cast them out of its congregations or severed ties with dissident churches, it remained without the power to persecute them. However, those called "heretics" were also called a number of other things (e.g. "fools," "wild dogs," "servants of Satan"), so the word "heretic" had negative associations from the beginning, and intentionally so.
In the middle of the 2nd century, three unorthodox groups of Christians adhered to a range of doctrines that divided the Christian communities of Rome: the teacher Marcion, the pentecostal outpourings of ecstatic Christian prophets of a continuing revelation, in a movement called "Montanism" because it had been initiated by Montanus and his female disciples, and the gnostic teachings of Valentinus. Early attacks upon alleged heresies formed the matter of Tertullian's Prescription Against Heretics (in 44 chapters, written from Rome), and of Irenaeus' Against Heresies (ca 180, in five volumes), written in Lyon after his return from a visit to Rome. The letters of Ignatius of Antioch and Polycarp of Smyrna to various churches warned against false teachers, and the Epistle of Barnabas accepted by many Christians as part of Scripture in the 2nd century, warned about mixing Judaism with Christianity, as did other writers, leading to decisions reached in the First Ecumenical Council, which was convoked by the Emperor Constantine at Nicea in 325, in response to further disruptive polemical controversy within the Christian community, in that case Arian disputes over the nature of the Trinity.
Irenaeus was the first to argue that the "proto-orthodox" position was the same faith that Jesus gave to the apostles, and that the identity of the apostles, their successors, and the teachings of the same were all well known public knowledge. This was therefore an earlier argument on the basis of Apostolic Succession. Irenaeus' opponents claimed to have received secret teachings from Jesus via other apostles which were not publicly known. (Gnosticism is predicated on the existence of hidden knowledge, but brief references to private teachings of Jesus have also survived in the canonic Scripture.) Irenaeus' opponents also claimed that the wellsprings of divine inspiration were not dried up, the doctrines of continuing revelation.
Before 325, the "heretical" nature of some beliefs was a matter of much debate within the churches. In the early church, heresies were sometimes determined by a selected council of bishops, or ecumenical council, such as the First Council of Nicea. After 325, some opinion was formulated as dogma through the canons promulgated by the councils. Each phrase in the Nicene Creed, which was hammered out at the Council of Nicea, addresses some aspect that had been under passionate discussion and closes the books on the argument, with the weight of the agreement of over 300 carefully selected bishops from around the empire. However, that did not prevent the Arians who were defeated at the council of 325 from dominating most of the church for the greater part of the fourth century, often with the aid of Roman emperors who favored them. In the East, the successful party of Cyril cast out Nestorius and his followers as heretics and collected and burned his writings.
The church had little power to actually punish heretics in the early years, other than by excommunication, a spiritual punishment, or, as in the case of Arius, assassination (Though this would me a matter of contention, as he was supported by the Royalty, and his end was rather strange. It is described as thus: As Arius was journeying to cocelebrate the Divine Liturgy with the Bishop, who had be pressured into doing such as a sign to the people that there wasn't really any difference between Arian and Church belief, tradition tell us Arius stopped to use the facilities. Some short time later his follower went in to check on him, as he had taken a long time. Apparently, his intestines had passed out of him.). To those who accepted it, an excommunication was the worst form of punishment possible, as it separated the individual from the body of Christ, his Church, and prevented salvation. Excommunication, or even the threat of excommunication, was enough to convince many a heretic to renounce his views. The Hispanic ascetic Priscillian of Avila was the first person to be executed for heresy, only sixty years after the First Council of Nicea, in 385. He was executed at the orders of Emperor Magnus Maximus, over the procedural objections of bishops Ambrose of Milan and Martin of Tours.
A number of the beliefs the Church has come to regard as heretical have to do with Christology, the nature of Jesus Christ and the relationship between Christ and God the Father. The historic teaching is that Christ was fully divine and at the same time fully human, and that the three persons of the Trinity are equal and eternal. Note that this position was not formally established as the orthodox position until it was challenged in the fourth century by Arius (Nicene Creed in 325); nor was the New Testament put into its present form until the end of the 4th century (Athanasius of Alexandria first lists the 27 books we have in the current New Testament in 367(?), but disputes continued.
Over the years, numerous Christian scholars and preachers have disagreed with the Church on various issues or doctrines. When the Church has become aware of these beliefs, they have been condemned as heretical. Historically, this often happened when the belief challenged, or was seen to challenge, Church authority, or drew a movement of followers who challenged the established order socially. For entirely secular reasons, some influential people have had an interest in maintaining the status quo or condemning a group they wished to be removed. The Church's internal explanations for its actions were based purely on objection to beliefs and philosophies that ran contrary to its interpretation of the Holy Scriptures and its official interpretation of Holy Tradition.
While the term is often used to indicate any nonorthodox belief such as Paganism, by definition heresy can only be committed by a person who considers himself a Christian, but rejects the teachings of the Christian Church. A person who completely renounces Christianity is not considered a heretic, but an apostate; a person who renounces the authority of the Church, but not its teachings, is a schismatic, while an individual outside of the Orthodox Church who considers himself to be Christian might be called Heterodox.
Heretics usually do not define their own beliefs as heretical. Heresy is the expression of a view from within an established belief system. For instance, Roman Catholics held Protestantism as a heresy while some non-Catholics considered Catholicism the "Great Apostasy."
- Some information in this article came from the Catholic Encyclopedia.