East Syriac Rite

The East Syriac Rite, or East Syrian Rite (also called the Edessan Rite, Assyrian Rite, Persian Rite, Chaldean Rite, Nestorian Rite, Babylonian Rite or Syro-Oriental Rite), is an Eastern Christian liturgical rite that employs the Divine Liturgy of Saints Addai and Mari and utilizes the East Syriac dialect as its liturgical language. It is one of the two main liturgical rites of Syriac Christianity, along with the West Syriac Rite (Syro-Antiochene Rite).

The East Syriac Rite originated in Edessa, Mesopotamia, and was historically used in the Church of the East—the largest branch of Christianity operating primarily east of the Roman Empire—, with pockets of adherents as far as South India, Central and Inner Asia, and a strong presence in the Sasanian (Persian) Empire. The Church of the East traces its origins to the 1st century, when Saint Thomas the Apostle and his disciples Saint Addai and Saint Mari brought the faith to ancient Mesopotamia (today's modern Iraq, eastern Syria, southeastern Turkey, and regions along the Turkish–Syrian and Iran–Iraq borders). According to traditional accounts, Thomas the Apostle is believed to have traveled as far as the Malabar coast of southwestern India. This account is not yet confirmed, as the earliest-record for an organised Christian presence in India is from the 6th century account of Alexandrian traveller Cosmas Indicopleustes.

The East Syriac rite remains in-use within churches descended from the Church of the East, namely the Assyrian Church of the East of Iraq (including its archdiocese, the Chaldean Syrian Church of India) and the Ancient Church of the East, as well as in two Eastern Catholic churches, the Chaldean Catholic Church of Iraq and the Syro-Malabar Church of India, which are both now in full communion with the See of Rome. The words of Institution are missing in the original version of the Liturgy of Saints Addai and Mari. However, the Eastern Catholic churches have added-in the words of Institution in their version of the liturgy.

Although Nestorius was condemned in 431 AD through the Council of Ephesus (resulting in a schism with the Catholic Church), the Assyrian Church Patriarch Mar Dinkha IV and Pope John Paul II signed a common declaration at the Vatican in 1994; the Common Christological Declaration (1994) document asserted that the split that occurred due to the Council of Ephesus in 431 AD was "due in large part to misunderstandings," affirmed for both that "Christ is true God and true man," recognized "each other as sister Churches" and vowed to resolve remaining differences. In 2001, the committee, established from the 1994 dialogue, drew-up guidelines for mutual admission to the Eucharist between the Chaldean Catholic Church and the Assyrian Church of the East, overcoming all other issues.

Versions of the East Syriac Rite are currently used by Churches descended from the erstwhile Church of the East:

The variety of terms used as designations for the rite reflects its complex history and consequent denominational diversity. The common term East Syriac Rite is based on the liturgical use of East Syriac dialect, and other terms reflect particular historical and denominational characteristics.

The Syrian and Mesopotamian Eastern Catholics were commonly called Chaldeans (or Assyro-Chaldeans). The term Chaldean, which in Syriac generally meant magician or astrologer, denoted in Latin and other European languages (Greater) Syrian nationality, and the Syriac or Aramaic language. For Aramaic, the designation "Chaldean" especially refers to the form that is found in certain chapters of Daniel. The broader usage of the term continued until the Latin missionaries at Mosul in the 17th century adopted "Chaldean" to distinguish the Catholics of the East Syriac Rite from those of the West Syriac Rite, which they called "Syrians". It was also used to distinguish from the Assyrian Church of the East, some of whom called themselves Suraye or even only "Christians", not with repudiating the theological name "Nestorian". Modern members of the Assyrian Church of the East and the Ancient Church of the East distinguish themselves from the rest of Christendom as the "Church of the East" or "Easterns" as opposed to "Westerns" by which they denote Greek Orthodox, Syriac Orthodox or Latin Catholics.

In recent times they have been called, chiefly by the Anglicans, the "Assyrian Church", a name which can be defended on archaeological grounds. Brightman, in his "Liturgies Eastern and Western", includes Chaldean and Malabar Catholics and Assyrians under "Persian Rite".