Heresy (/ˈhɛrəsi/) is any belief or theory that is strongly at variance with established beliefs or customs, in particular the accepted beliefs of a church or religious organization. A heretic is a proponent of such claims or beliefs. Heresy is distinct from both apostasy, which is the explicit renunciation of one's religion, principles or cause, and blasphemy, which is an impious utterance or action concerning God or sacred things.Heresy, from Greek αἵρεσις, originally meant 'choice' or 'thing chosen', but it came to mean the 'party or school of a man's choice' and also referred to that process whereby a young person would examine various philosophies to determine how to live. The word 'heresy' is usually used within a Christian, Jewish, or Islamic context, and implies slightly different meanings in each. The founder or leader of a heretical movement is called a heresiarch, while individuals who espouse heresy or commit heresy are known as heretics. Heresiology is the study of heresy.According to Titus 3:10 a divisive person should be warned twice before separating from him. The Greek for the phrase 'divisive person' became a technical term in the early Church for a type of 'heretic' who promoted dissension. In contrast correct teaching is called sound not only because it builds up the faith, but because it protects it against the corrupting influence of false teachers.The Baha'i Faith is considered an Islamic heresy in Iran. To Mughal Emperor Aurangzeb, Sikhs were heretics.Orthodox Judaism considers views on the part of Jews who depart from traditional Jewish principles of faith heretical. In addition, the more right-wing groups within Orthodox Judaism hold 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 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.The act of using Church of Scientology techniques in a form different than originally described by L. Ron Hubbard is referred to within Scientology as 'squirreling' and is said by Scientologists to be high treason. The Religious Technology Center has prosecuted breakaway groups that have practiced Scientology outside the official Church without authorization.In other contexts the term does not necessarily have pejorative overtones and may even be complimentary when used, in areas where innovation is welcome, of ideas that are in fundamental disagreement with the status quo in any practice and branch of knowledge. Scientist/author Isaac Asimov considered heresy as an abstraction, mentioning religious, political, socioeconomic and scientific heresies. He divided scientific heretics into endoheretics (those from within the scientific community) and exoheretics (those from without). Characteristics were ascribed to both and examples of both kinds were offered. Asimov concluded that science orthodoxy defends itself well against endoheretics (by control of science education, grants and publication as examples), but is nearly powerless against exoheretics. He acknowledged by examples that heresy has repeatedly become orthodoxy.