Heresy is a controversial or novel change to a system of beliefs, especially a religion, that conflicts with established dogma. It is distinct from apostasy, which is the formal denunciation of one's religion, principles or cause, and blasphemy, which is irreverence toward religion. The founder or leader of a heretical movement is called a heresiarch, while individuals who espouse heresy are known as heretics. Heresiology is the study of heresy.
The word "heresy" comes from the Greek hairetikos "able to choose" (haireisthai "to choose"). The term heresy is often perceived as a value judgment and the expression of a view from within an established belief system.
According to Merriam-Webster: from Late Latin haeresis, from Late Greek hairesis, from Greek, "action of taking, choice, sect", from hairein "to take".
The use of the word "heresy" in the context of Christianity was given wide currency by Irenaeus in his tract Contra Haereses (Against Heresies) to describe and discredit his opponents in the early Christian Church. He described his own position as orthodox (from ortho- "straight" + doxa "belief") and his position eventually evolved into the position of the early Christian Church.
Heretics usually do not perceive their own beliefs as heretical. For instance, some Roman Catholics hold Protestantism as a heresy while some non-Catholics considered Catholicism the "Great Apostasy." For a heresy to exist there must be an authoritative system of dogma designated as orthodox, such as those proposed by Catholicism.
The first known usage of the term in a civil legal context was in 380 AD by the "Edict of Thessalonica" of Theodosius I. Prior to the issuance of this edict, the Church had no state sponsored support for any particular legal mechanism to counter what it perceived as 'heresy'. By this edict, in some senses, the line between the Christian Church and the Roman State was blurred. One of the outcomes of this blurring of Church and State was a sharing of State powers of legal enforcement between Church and State authorities. At its most extreme reach, this new Church authority of legal enforcement gave Church leaders the power to pronounce the death sentence upon those whom they might perceive to be 'heretics'.
Within 5 years of the official 'criminalization' of heresy by the emperor, the first Christian heretic, Priscillian was executed in 385 by Roman officials. For some years after the reformation, Protestant Churches were also known to execute those whom they considered as heretics, witness the Salem witch trials. The last known heretic executed by sentence of the Roman Catholic Church was Cayetano Ripoll in 1826. The number of people executed as heretics under the authority of the various 'church authorities' is not known, however it most certainly numbers into the several thousands.
Perhaps due to the many modern negative connotations associated the term 'heretic', such as the Spanish inquisition, the term is used less often today. There are however, some notable exceptions: see for example Rudolf Bultmann and the "character" of debates over ordination of women and gay priests.
Orthodox Judaism considers views on the part of Jews which depart from the traditional Jewish principles of faith to be heretical. In addition, the more right-wing groups within Orthodox Judaism holds that all Jews who reject the simple meaning of Maimonides's 13 principles of Jewish faith are heretics. As such, most of Orthodox Judaism considers Reform and Reconstructionist Judaism to be heretical movements, and regards most of Conservative Judaism as heretical. The liberal wing of Modern Orthodoxy is more tolerant of Conservative Judaism, particularly its right wing, as there is some theological and practical overlap between these groups.
Heresy in Islam
Many in the two main bodies of Islam—Sunnis and the Shi'as—have regarded the other as heretical. Groups like the Ismailis, the Hurufiya, the Alawis, the Bektashi and even the Sufis have also been regarded as heretical by some. Although Sufism is often accepted as valid by Shi'a and many Sunnis, the relatively recent movement of Wahhabism view it as heretical.
- Definition of "heresy" at Free Online Dictionary
- Definition of "apostasy" at Dictionary.com
- Definitions of "blasphemy" at Dictionary.com
- The Limits of Orthodox Theology: Maimonides' Thirteen Principles Reappraised, by Marc B. Shapiro, ISBN 1874774900, A book written as a contentious rebuttal to an article written in the Torah UMadda Journal.