When we find it said that his works were esteemed as highly as the Pitakas, or that the documents which he translated into Pali were the words of the Buddha,[81] the suspicion naturally arises that the Pali Canon may be in part his composition and it may be well to review briefly its history in Ceylon.  Our knowledge appears to be derived entirely from the traditions of the Mahavihara which represent Mahinda as teaching the text of the Pitakas orally, accompanied by a commentary.  If we admit the general truth of the narrative concerning Mahinda’s mission, there is nothing improbable in these statements, for it would be natural that an Indian teacher should know by heart his sacred texts and the commentaries on them.  We cannot of course assume that the Pitakas of Mahinda were the Pali Canon as we know it, but the inscriptions of Asoka refer to passages which can be found in that canon and therefore parts of it at any rate must have been accepted as scripture in the third century B.C.  But it is probable that considerable variation was permitted in the text, although the sense and a certain terminology were carefully guarded.  It was not till the reign of Vattagamani, probably about 20 B.C., that the canon was committed to writing and the Parivara, composed in Ceylon,[82] was included in it.

In the reign of Buddhadasa[83] a learned monk named Mahadhammakathi is said to have translated the Suttas into Sinhalese, which at this time was esteemed the proper language for letters and theology, but in the next century a contrary tendency, probably initiated by Buddhaghosa, becomes apparent and Sinhalese works are rewritten in Pali.[84] But nothing indicates that any part of what we call the Pali Canon underwent this process.  Buddhaghosa distinguishes clearly between text and comment, between Pali and Sinhalese documents.  He has a coherent history of the text, beginning with the Council of Rajagaha; he discusses various readings, he explains difficult words.  He treated the ancient commentaries with freedom, but there is no reason to think that he allowed himself any discretion or right of selection in dealing with the sacred texts accepted by the Mahavihara, though it might be prudent to await the publication of his commentaries on all the Nikayas before asserting this unreservedly.

To sum up, the available evidence points to the conclusion that in the time of Asoka texts and commentaries preserved orally were brought to Ceylon.  The former, though in a somewhat fluid condition, were sufficiently sacred to be kept unchanged in the original Indian language, the latter were translated into the kindred but still distinct vernacular of the island.  In the next century and a half some additions to the Pali texts were made and about 20 B.C. the Mahavihara, which proved as superior to the other communities in vitality as it was in antiquity, caused written copies to be made of what it considered as the canon, including some recent works.  There is no evidence that Buddhaghosa or anyone else enlarged or curtailed the canon, but the curious tradition that he collected and burned all the books written by Mahinda in Sinhalese[85] may allude to the existence of other works which he (presumably in agreement with the Mahavihara) considered spurious.