Christianity, like other western ideas, may have reached India both by land and by sea.  After the conquests of Alexander had once opened the route to the Indus and established Hellenistic kingdoms in its vicinity, the ideas and art of Greece and Rome journeyed without difficulty to the Panjab, arriving perhaps as somewhat wayworn and cosmopolitan travellers but still clearly European.  A certain amount of Christianity may have come along this track, but for any historical investigation clearly the first question is, what is the earliest period at which we have any record of its presence in India?  It would appear[1073] that the first allusions to the presence of Christians in Parthia, Bactria and the border lands of India date from the third century and that the oldest account[1074] of Christian communities in southern India is the narrative of Cosmas Indicopleustes (c. 525 A.D.).  These latter Christians probably came to India by sea from Persia in consequence of the persecutions which raged there in 343 and 414, exactly as at a later date the Parsees escaped the violence of the Moslims by emigrating to Gujarat and Bombay.

The story that the Apostle Thomas preached in some part of India has often been used as an argument for the early introduction and influence of Christianity, but recent authorities agree in thinking that it is legendary or at best not provable.  The tale occurs first in the Acts of St. Thomas,[1075] the Syriac text of which is considered to date from about 250.  It relates how the apostle was sold as a slave skilled in architecture and coming to the Court of Gundaphar, king of India, undertook to build, a palace but expended the moneys given to him in charity and, when called to account, explained that he was building for the king a palace in heaven, not made with hands.  This sounds more like an echo of some Buddhist Jataka written in praise of liberality than an embellishment of any real biography.  Other legends make southern India the sphere of Thomas’s activity, though he can hardly have taught in both Madras and Parthia, and a similar uncertainty is indicated by the tradition that his relics were transported to Edessa, which doubtless means that according to other accounts he died there.  Tradition connects Thomas with Parthians quite as much as with Indians, and, if he really contributed to the diffusion of Christianity, it is more likely that he laboured in the western part of Parthia than on its extreme eastern frontiers.  The fact that there really was an Indo-Parthian king with a name something like Gondophares no more makes the legend of St. Thomas historical than the fact that there was a Bohemian king with a name something like Wenceslas makes the Christmas carol containing that name historical.

On the other hand it is clear that during the early centuries of our era no definite frontier in the religious and intellectual sphere can be drawn between India and Persia.  Christianity reached Persia early:  it formed part of the composite creed of Mani, who was born about 216, and Christians were persecuted in 343.  From at least the third century onwards Christian ideas may have entered India, but this does not authorize the assumption that they came with sufficient prestige and following to exercise any lively influence, or in sufficient purity to be clearly distinguished from Zoroastrianism and Manichaeism.