The Church of the East traces its origins to the See of Seleucia-Ctesiphon, said to be founded by Thomas the Apostle.
Other founding figures are Saint Mari and Saint Addai as evidenced in the Doctrine of Addai and the Holy Qurbana of Addai and Mari.
Around AD 522, an Egyptian monk, Cosmas Indicopleustes, visited the Malabar Coast.
He mentions Christians in Malabar (Kerala), in his book Christian Topography.
Though the Saint Thomas Christians welcomed them, these bishops had not made any effort to subjugate them.
Saint Thomas Christians remained as an independent group, and they got their bishops from Church of the East until the 16th century.
According to the 1st century annals of Pliny the Elder and the author of Periplus of the Erythraean sea, Muziris in Kerala could be reached in 40 days' time from the Egyptian coast purely depending on the South West Monsoon winds.
He found that they were using the Gospel of Matthew in the Hebrew language.(a landmark split leading to a public Oath known as Coonen Cross Oath), reformative activities during the time of the British (6,000 - 12,000 Jacobites joined the C. After the 8th century when Hindu Kingdoms came to sway, Christians were expected to strictly abide by stringent rules pertaining to caste and religion. The Archdeacon was the head of the Church, and Palliyogams (Parish Councils) were in charge of temporal affairs.They had a liturgy-centered life with days of fasting and abstinence.The First Council of Nicaea, held in Nicaea in Bithynia (present-day İznik in Turkey), convoked by the Roman Emperor Constantine I in 325, was the first Ecumenical council of the Christian Church, and most significantly resulted in the first uniform Christian doctrine, called the Nicene Creed.It is documented that Mar John, the Bishop of Great India attended the council.Their language is Malayalam, the language of Kerala.