Heresy

The English word “heresy” comes from the Ancient Greek *haíresis*, meaning “choice” or “thing chosen.” Over time, it came to refer to a “party or school of one’s choice” and also described a young person’s process of examining various philosophies to decide how to live. The term is most often used in Christian, Jewish, or Islamic contexts, with slightly different nuances in each. The founder or leader of a heretical movement is called a heresiarch; individuals who adopt or commit heresy are heretics.

In Christianity, the apostle Paul’s letter to Titus (3:10) advises warning a divisive person twice before separating from them. The Greek term for “divisive person” became a technical label in the early Church for a heretic who fostered dissension. Correct teaching was called “sound” because it strengthened orthodox belief and guarded against the “corrupting” influence of heretical teachers. Tertullian (c. AD 155–240) suggested that Jews most inspired heresy in Christianity, arguing that heretics followed Jewish guidance in denying Jesus as the Christ—since he saw Christianity not as a separate religion but as a continuation of Judaism with its messianic promise fulfilled.

Irenaeus popularized the use of “heresy” in his 2nd-century work *Contra Haereses* (Against Heresies) to discredit opponents in the early Christian community. He labeled the community’s beliefs as orthodox (from Greek *orthos*, “straight,” and *doxa*, “belief”) and the Gnostics’ teachings as heretical, also invoking apostolic succession to support his case. Constantine the Great, who with Licinius issued the Edict of Milan granting toleration to Christianity and was the first Roman emperor baptized, set precedents for later policy. As Roman emperor, he held the title Pontifex Maximus, high priest of all recognized religions. To settle the doctrinal dispute started by Arius, Constantine convened the first ecumenical council and enforced orthodoxy through imperial authority.

The first known legal use of “heresy” came in AD 380 with the Edict of Thessalonica by Theodosius I, which made Christianity the state church of the Roman Empire. Before this edict, the Church had no state-backed legal mechanism to counter heresy. The edict blurred the lines between state and church authority, sharing state enforcement powers with church authorities. Within six years, the first Christian heretic executed, Priscillian, was condemned in 386 by Roman secular officials for sorcery and put to death with four or five followers. His accusers were excommunicated by both Ambrose of Milan and Pope Siricius, who opposed Priscillian’s heresy but believed capital punishment was inappropriate and usually evil. Theodosius II’s edict in 435 imposed severe penalties on those who possessed or spread writings of Nestorius, and those with writings of Arius were sentenced to death.

In the 7th-century text *Concerning Heresy*, Saint John of Damascus labeled Islam a Christological heresy, calling it the “heresy of the Ishmaelites.” This view remained popular in Christian circles into the 20th century, held by theologians like Congregationalist cleric Frank Hugh Foster and Roman Catholic historian Hilaire Belloc, who described it as “the great and enduring heresy of Mohammed.” After the Reformation, Protestant churches also executed heretics; for instance, Michael Servetus was declared a heretic by both the Reformed and Catholic Churches for rejecting the doctrine of the Holy Trinity. The last known heretic executed by Catholic Church sentence was Spanish schoolmaster Cayetano Ripoll in 1826. The total number of people executed as heretics under ecclesiastical authority is unknown.

Though less common today, formal heresy charges still occur in Christian churches. In Protestant churches, issues have included modern biblical criticism and the nature of God. In the Catholic Church, the Congregation for the Doctrine of the Faith criticizes writings for “ambiguities and errors” without using the word “heresy.” On 11 July 2007, Pope Benedict XVI stated that some Protestant groups are “ecclesial communities” rather than Churches. Representatives of those denominations accused the Vatican of effectively calling them heretics. The Pope clarified that the phrase did not imply explicit heresy, only that the communities lacked certain “essential elements” of an apostolic church.