Orthodoxy needs a rulebook, which is why some traditions barely have one
Orthodoxy comes from Greek for correct opinion, and it only works where a community has agreed on what correct means. Christianity fought for centuries over its definition; Hinduism, with no founder or central authority, arguably has no orthodoxy at all; and even the ancient Epicureans spoke of uttering correct philosophy.
The word describes adherence to an accepted creed, and its most famous battles were Christian. Early councils had to choose between the view of Athanasius and Eustathius, that the Son shares the same essence as the Father, and the teaching of Arius and Eusebius of Nicomedia, that he differs in essence. The first became Trinitarian doctrine and, reinforced by the Council of Ephesus in 431, claimed the name orthodox; nontrinitarian Christians still dispute that label.
Later splits turned the adjective into a church name. After Chalcedon in 451, the Oriental Orthodox kept orthodox as a badge of their tradition. After the Great Schism of 1054, both Rome and the East considered themselves the true orthodox and catholic church, but over time Western Europeans came to use Catholic for the West and Orthodox for the East, although both adjectives had been in church use since the 2nd and 4th centuries. Protestants had their own orthodox eras: Lutheran orthodoxy ran from the Book of Concord in 1580 until the Enlightenment.
Other traditions fit the idea unevenly. Theravada Buddhism, with its strict loyalty to the Pali Canon and monastic discipline, is called the most orthodox Buddhist school, even though the Buddha warned against clinging to scripture in the Kalama Sutta. Sunni Islam is sometimes termed orthodox, though the scholar John Burton doubted any such thing exists. In Indian philosophy the nearest match is āstika, schools that accept the authority of the Vedas, as opposed to nāstika ones.
Orthodoxy presupposes shared standards for judging belief, and where thought has not been standardised it cannot take hold; writing helped by fixing scriptures into canons. Outside religion the word often carries a slight sting, describing received wisdom under challenge, while an unorthodox fix is simply an unusual one. Modern movements adopt it too, including Kemetic Orthodoxy, a reconstruction of ancient Egyptian religion, and some groups within Slavic Native Faith.
Source: Orthodoxy
