Heresy in Christianity

When heresy is used today with reference to Christianity, it denotes the formal denial or doubt of a core doctrine of the Christian faith as defined by one or more of the Christian churches. It should be distinguished from both apostasy and schism, apostasy being nearly always total abandonment of the Christian faith after it has been freely accepted, and schism being a formal and deliberate breach of Christian unity and an offence against charity without being based essentially on doctrine.

In Western Christianity, heresy most commonly refers to those beliefs which were declared to be anathema by any of the ecumenical councils recognized by the Catholic Church. In the East, the term "heresy" is eclectic and can refer to anything at variance with Church tradition. Since the Great Schism and the Protestant Reformation, various Christian churches have also used the concept in proceedings against individuals and groups deemed to be heretical by those churches.

The Catholic Church distinguishes between "formal heresy" and "material heresy". The former involves willful and persistent adherence to an error in matters of faith and is a grave sin and produces excommunication. "Material heresy" is the holding of erroneous opinions through no fault of one's own and is not sinful. Protestants can fall into either the first or the second group, depending on whether they are in invincible ignorance while the Eastern Orthodox are considered to be schismatic but are recognised as local churches, but "defective" (according to Dominus Iesus) and severed from the Catholic Church, which in Catholic teaching is the "only true Church".

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