At a Synod held at Spalatro in Dalmatia, in A.D. 1060, Methodius, notwithstanding he had been patronized by several popes, was declared a heretic, nearly two hundred years after his death; and it was resolved that henceforth no mass should be read except in the Latin or Greek language.  From the decrees of that Synod, it appears that they took the Gothic and Slavonic for the same idiom.  A great part of the inhabitants of Illyria remained nevertheless faithful to their language, and to a worship familiar to their minds through that language.  A singular means, Dobrovsky asserts, was found by some of the shrewder priests, to reconcile their inclinations with the jealous despotism of Rome.  A new alphabet was invented, or rather the Cyrillic letters were altered and transformed in such a way, as to approach in a certain measure to the Coptic characters.  To give some authority to the new invention, it was ascribed to St. Jerome.  This, it was maintained, is the Glagolitic alphabet, so called, used by the Slavic priests of Dalmatia and Croatia until the present time.  Cyril’s translation of the Bible and the liturgic books were copied in these characters, with a very few deviations in the language; which probably had their foundation in the difference of the Dalmatian dialect, or were the result of the progress of time; for this event took place at least 360 years after the invention of the Cyrillic alphabet.  With this modification, the priests succeeded in satisfying both the people and the chair of Rome.  It sounded the same to the people, and looked different to the pope.  The people submitted easily to the ceremonies of the Romish worship, if only their beloved language was preserved; and the pope, fearing justly the transition of the whole Slavic population of those provinces to the Greek church, permitted the mass to be read in Slavonic, in order to preserve his influence in general.

This hypothesis had come to be pretty generally received; when in the year 1830, some Glagolitic manuscripts, which bore very decided evidence of being at least as old as the middle of the eleventh century, were discovered by Kopitar in the library of Count Clotz in Tyrol.  The existence of the calumniated alphabet at a period cotemporary with the oldest Cyrillic manuscript known (the Evangelium of Ostromir), was a death-blow to the above singular narrative.  Kopitar published the newly discovered Codex, accompanied by a thundering philippic against the defenders of the former theory, and in favour of the antiquity of the Glagolitic alphabet, and of the Pannonian origin of the Slavic liturgy.[16] But here the matter rested.  Nothing has since been discovered, (so far as we are informed,) to throw light on the first invention or introduction of this alphabet; no connecting link to explain its relation to the Cyrillic forms of writing.

According to Vostokof, a Russian scholar of great learning, and one of the principal names in Old Slavic literature,[17] the history of the Old Slavic or Church language and its literary cultivation, may be divided into three periods: