Apostasy is the renunciation, either through words or actions, of a religious faith. One who commits apostasy is declared apostate, or excommunicated, by the church or religious institution. This means the person may no longer receive access to God by receiving communion or other sacraments. It is similar to the Amish practice of "shunning," although shunning means the apostate is completely ignored, even in civil intercourse. The object is the same. Wayward apostates are placed "outside the camp" to convince them of the error of their ways so they will eventually return. Biblical support for the practice is found in Paul's letters to the Corinthians, but it in fact preceded the Christian New Testament.
The term is first found in the Greek Septuagint version of scripture, used in various apocryphal books as well as in Joshua and Jeremiah. But it was commandeered early in the Christian era, first applied to no less a luminary than the apostle Paul himself in Acts 21:21. Paul turned the tables on his accusers when he wrote to the Thessalonians. In an apocalyptic passage later echoed by the author of 2 Peter, Paul assured Christians that the "apostasy" or rebellion must come first, before the return of the Lord. Since it certainly wasn't his own apostasy he was referring to, he was, in effect, calling his accusers apostate themselves.
exclusion from a religious community, widely used in the past as a punitive measure by Catholicism, Orthodoxy, Judaism, and certain other religions.
Excommunication was used by churches for political purposes, particularly for the struggle against popular and revolutionary movements. Among those excommunicated by the Russian Orthodox Church were S. T. Razin, E. I. Pugachev, and L. N. Tolstoy; the Catholic Church excommunicated Jan Hus and Giordano Bruno; the Jewish rabbis excommunicated B. Spinoza. In 1949 and 1959 the Vatican announced the excommunication of Catholics who were taking part in the communist movement or cooperating with it.