While comparative linguistics could in this way firmly establish that a certain source state, roughly along the Erasmian model, had once obtained, and that significant changes had to have occurred later, during the development towards Modern Greek, the comparative method had less to say about the question "when" these changes took place. Erasmus had been eager to find a pronunciation system that corresponded most closely to the written letters, and it was now natural to assume that the reconstructed sound system was that which obtained at the time when Greek orthography was in its formative period. For a time, it was taken for granted that this would also have been the pronunciation valid for all the period of classical literature. However, it was perfectly possible that the pronunciation of the living language had begun to move on from that reconstructed system towards that of Modern Greek, possibly already quite early during antiquity.