Heresy

Heresy refers to any belief or theory that strongly disagrees with established customs or accepted religious laws.

Within a religious organization, a heretic is a person who supports these opposing ideas. The leader of a movement centered on such ideas is known as a heresiarch. The study of these disagreements is called heresiology. It is important to distinguish heresy from other concepts. Apostasy is the explicit act of renouncing one's religion or principles. Blasphemy refers to impious actions or words concerning sacred things. The word itself comes from the Ancient Greek term *haíresis*, which originally meant "choice" or "a thing chosen." Over time, it came to represent a person's chosen school of thought or philosophy.

In the context of major faiths like Judaism, Christianity, and Islam, the term carries specific weight. In early Christianity, thinkers often described correct teaching as "sound." This term suggested that true belief was strong and protected the community from corruption. Irenaeus, a 2nd-century figure, used the term "orthodox" to describe the community's official doctrines. This word comes from the Greek *orthos*, meaning "straight," and *doxa*, meaning "belief." Irenaeus used his writings to discredit opponents, such as the Gnostics. He argued for the importance of apostolic succession to maintain these correct beliefs.

The relationship between religious belief and government power changed the history of heresy. In the Roman Empire, Emperor Constantine the Great sought to end doctrinal debates, such as those started by Arius. He called ecumenical councils to resolve these issues and enforce orthodoxy for the sake of domestic peace. In AD 380, the Edict of Thessalonica made Christianity the state church of the Roman Empire. This created an overlap between the authority of the state and the Church. Consequently, the state began to share its legal enforcement powers with religious authorities. One of the first documented results of this was the execution of Priscillian in AD 386. Though Roman officials executed him for sorcery, he was a Christian heretic. Interestingly, religious leaders like Ambrose of Milan and Pope Siricius opposed his execution, viewing capital punishment as evil.

Throughout history, different groups and individuals have faced severe consequences for their views.

In the 16th century, the German friar Martin Luther was excommunicated by Pope Leo X in 1520. During the Reformation, some Protestant churches also executed those they labeled heretics. For instance, Michael Servetus was declared a heretic by both Catholic and Reformed churches for rejecting the doctrine of the Holy Trinity. Other movements, such as the Cathars in France, grew into large mass movements. The Church eventually initiated the Albigensian Crusades to eliminate the Cathar heresy.

In other instances, such as the case of the Amalricians in 1210, heretics were put to death by burning.

Scientific discovery has also intersected with religious definitions of heresy.

The scientist Galileo Galilei was famously brought before the Inquisition. He was considered "vehemently suspect of heresy" because of his views on the universe. Specifically, he held that the Sun was at the center of the universe and the Earth moved. The authorities believed these opinions contradicted Holy Scripture. To resolve the matter, Galileo was required to abjure, curse, and detest his own findings. He spent the remainder of his life under house arrest. While this was a major event, many historians view the Galileo affair as an exception in the relationship between science and faith.

In the Catholic Church, the definition of heresy remains part of its legal framework. The 1983 Code of Canon Law defines it as the obstinate denial or doubt of a truth that must be believed by divine and Catholic faith. This occurs after a person has received baptism. Such actions can lead to automatic excommunication, known as *latae sentais*. Historically, the Church dealt with various small sects, including Arianism, Pelagianism, and Donatism. In the 6th century, the *Codex Justinianus* even defined heretics as those not devoted to the Catholic Church, preventing them from holding authority in the Eastern Roman Empire.

In modern times, the way religious institutions handle disagreement has evolved.

Formal charges of heresy are much less common today. In Protestant circles, discussions often focus on biblical criticism or the nature of God. The Catholic Church's Congregation for the Doctrine of the Faith may criticize writings for errors or ambiguities without explicitly using the word "heresy." For example, in 2007, Pope Benedict XVI referred to certain Protestant groups as "ecclesial communities" rather than "Churches." He clarified that this was not an accusation of explicit heresy, but rather a statement that these groups lacked certain essential elements of an apostolic church.