An ancient sect, who early in the middle ages were numerous in Persia and still survive in India, claim St. Thomas as their founder; but many theologians consider the account of the labours of St. Thomas in India as having been invented by the Manichaeans, and as early as the 5th century the Thomas of India was regarded by Theodoret as a disciple of Manes. – American Cyclopaedia
Thomas also called Didymus, one of the twelve apostles. Both names, the Hebrew Thomas (Th’om) and the Greek Didymus, denote a twin. Thomas is rarely mentioned in the New Testament, and little is known of him. The principal traits of his character are given in the Gospel of John. When Jesus after his crucifixion appeared to his disciples, Thomas was not present, and refused to believe until he himself saw and touched Jesus. As to the scene of his apostolic labours, the statements of the ecclesiastical writers of the first centuries do not agree; according to some it was Parthia, according to others Egypt and Ethiopia, and according to others India, where the Portuguese in the 16th century asserted that they had found his body. An ancient sect who early in the middle ages were numerous in Persia and still survive in India, claim St. Thomas as their founder; but many theologians consider the account of the labors of St. Thomas in India as having been invented by the Manichaeans, and as early as the 5th century the Thomas of India was regarded by Theodoret as a disciple of Manes. To the apostle Thomas an Evangelium Infantioe Christi (also Evangelium secundum Thomam) is ascribed, which pretends to fill up the gaps left by the canonical Gospels in the time from the infancy of Jesus until his public appearance; but it has always been regarded as apocryphal. (See Thilo, Acta Thomas Apostoli, Leipsic, 1823.) St. Thomas is commemorated in the Roman Catholic Church on Dec. 21; in the Greek Church on the first Sunday of her Church year, beginning with Easter (hence called Thomas Sunday). – From the American Cyclopaedia entry for Saint Thomas
ACTA INDICA 