In religion, heterodoxy (from Ancient Greek: , "other, another, different" + , "popular belief") means "any opinions or doctrines at variance with an official or orthodox position". Under this definition, heterodoxy is similar to unorthodoxy, while the adjective 'heterodox' could be applied to a dissident.
Heterodoxy is also an ecclesiastical term of art, defined in various ways by different religions and churches. For example, in the apostolic churches (the Eastern Orthodox Church, the Roman Catholic Church, the Church of the East, the Anglican Communion, and the Oriental Orthodox Churches), heterodoxy may describe beliefs that differ from strictly orthodox views, but that fall short either of formal or of material heresy.
In the Eastern Orthodox Church, the term is used primarily in reference to Christian churches and denominations not belonging to the communion of Eastern Orthodox churches and espousing doctrines contrary to the received Holy Tradition. It also describes any theological position, moral principle, spiritual practice, or lifestyle thought to be inconsistent with the Catholic Rule of Faith. In general, this term is used in two distinct senses:
To label a theological system or viewpoint which, although erroneous and unacceptable to hold or promote within Orthodoxy, has not been formally defined as heresy.
To label a theological system or viewpoint which is both contrary to Orthodoxy and whose adherents have not been baptized into the Church, so that the attribution of heresy would be improper.
Heterodoxy in the Roman Catholic Church refers to views that differ from strictly orthodox views, but retain sufficient faithfulness to the original doctrine to avoid heresy. Many Roman Catholics profess some heterodox views, either on doctrinal or social issues.
Many Protestants, such as Lutherans, consider Christian teachings which are not in agreement with their understanding of scripture to be heterodoxical. As Charles Spurgeon says:
[Y]ou shall find spiritual life in every church.