The term heresy comes from the Greek haireisthai, which means to choose. It came to refer to the act of holding very unorthodox and/or unpopular religious opinions. Technically speaking, then, heresy is not so much the rejection of a religious authority as it is the rejection of a particular religious authority in favor of some other religious authority.
Nevertheless, the labeling of some position as heresy implies the rejection of the legitimate religious authority in favor of some illegitimate authority. This means that questions about the relationship between heretical and orthodox religious opinions involves, at their core, questions about the nature of legitimate authority and who is justified in speaking on behalf of a religious community.
In the Acts of the Apostles it is used to refer to a sect, but without reference to its character. In Pauls epistles, however, it acquires a more negative character. Paul lists heresieswith other crimes and seditions (Gal. 5:19-21):
- Now the works of the flesh are manifest, which are these; Adultery, fornication, uncleanness, lasciviousness, Idolatry, witchcraft, hatred, variance, emulations, wrath, strife, seditions, heresies, Envyings, murders, drunkenness, revellings, and such like: of the which I tell you before, as I have also told you in time past, that they which do such things shall not inherit the kingdom of God.
As the Christian Church became more organized and doctrine became a more imporant means for identifying Christians, the concept of heresy came to be used to denote divisions or schisms within the church (1 Cor. 11:18-19):
- For first of all, when ye come together in the church, I hear that there be divisions among you; and I partly believe it. For there must be also heresies among you, that they which are approved may be made manifest among you.
In Titus 3:10 a heretical person is described as one who chooses to follow his own self-willed questions, and is therefore to be avoided. Heresies in Christianity thus came to refer to self-chosen doctrines not emanating from God (2 Pet. 2:1): But there were false prophets also among the people, even as there shall be false teachers among you, who privily shall bring in damnable heresies, even denying the Lord that bought them, and bring upon themselves swift destruction.
Early Christianity treated heresy negatively and the punishment was usually some sort of reproof or, at most, excommunication. So long as Christianity itself was persecuted or powerless, greater freedom of thought was tolerated. However, once Chrisitanity became the state religion, disagreements over doctrine became threats to political and social stability in the empire. As a consequence, those who failed to uphold orthodoxy and fell into heresy were treated as enemies of the social order, and tolerance of differences of opinion was no longer very great.
As Christianity became more powerful and more responsible for the workings of society, its doctrines also grew more complex. One consequence of this was that the ways in which a person could fall into either heresy or apostasy grew in number and, so, Christian authorities also had to improve upon their abilities to detect and punish both. A primary tool for the detection and punishment of both heresy and apostasy was the Inquisition.

