Dogma, from the Greek δόγμα, plural δόγματα and of which the plural is either dogmata or dogmas, is the established belief or doctrine held by a religion, ideology, or organization that is thought to be authoritative and cannot to be disputed or doubted. In the context of religion the term is largely descriptive, but outside of religion its current usage tends to carry a pejorative connotation — referring to concepts as being "established" only according to a particular point of view, and thus one of doubtful foundation. This pejorative connotation is even stronger with the term dogmatic, when it is used to describe a person of rigid beliefs who is not open to rational argument.
The word dogma was used by the ancient classical writers as an opinion or as a truth to a person as in philosophical doctrines, particularly those philosophical doctrines of particular schools of philosophers. The word was used as well to signify a public decree or ordinance. It is used in the Holy Scripture, in the sense of a decree or civil edict as in Luke 2:1: “And it came to pass, that in those days that there went out a decree (dogma) from Caesar Augustus”; in the sense of an ordinance of the Mosaic Law as in Eph. 2:15: “Having abolished in the flesh the enmity, even the law of commandments contained in ordinances (dogmasin); and as applied to the ordinances or decrees of the first Apostolic Council in Jerusalem: “And as they went through the cities, they delivered them the decrees (dogmata) for to keep, that were ordained of the apostles and elders which were at Jerusalem.“ (Acts 16:4).
Among the early Church Fathers the word dogma was used most often for the doctrines and moral precepts taught by Christ and the Holy Apostles with a distinction made for dogmas as having been taught by Christ, by the Apostles, and having come from the Church.
But according to long-standing usage a dogma is now understood to be a truth appertaining to faith or morals, revealed by God, transmitted from the Apostles in the Scriptures or by tradition, and proposed by the Church for the acceptance of the faithful. It might be described briefly as a revealed truth defined by the Church -- but private revelations do not constitute dogmas, and some theologians confine the word defined to doctrines solemnly defined by general councils, while a revealed truth becomes a dogma when proposed by the Church through her teaching office. A dogma therefore implies a twofold relation: to Divine revelation and to the authoritative teaching of the Church.
For Orthodox Christians, the dogmata are contained in the Nicene Creed and the canons of the seven ecumenical councils. These tenets are summarized by St. John of Damascus in his Exact Exposition of the Orthodox Faith, which is the third book of his main work, titled The Fount of Knowledge. In this book he takes a dual approach in explaining each article of the Orthodox faith: one for Christians, where he uses quotes from Scripture and, occasionally, from works of other Fathers of the Church, and the secondly, directed both at non-Christians (but who, nevertheless, hold some sort of religious belief) and at atheists, where he quite skillfully employs Aristotelian logic and dialectics, especially reductio ad absurdum.