In the five centuries between Caesar's conquest and the collapse of the Western Roman Empire, the Gaulish language and cultural identity underwent a syncretism with the Roman culture of the new governing class, and evolved into a hybrid Gallo-Roman culture that eventually permeated all levels of society. Gauls continued writing some inscriptions in the Gaulish language, but switched from the Greek alphabet to the Latin alphabet during the Roman period. Current historical research suggests that Roman Gaul was "Roman" only in certain (albeit major) social contexts, the prominence of which in material culture has hindered a better historical understanding of the permanence of many Celtic elements. The Roman influence was most apparent in the areas of civic religion and administration. The Druidic religion was suppressed by Emperor Claudius I, and in later centuries Christianity was introduced. The prohibition of Druids and the syncretic nature of the Roman religion led to disappearance of the Celtic religion. It remains to this day poorly understood: current knowledge of the Celtic religion is based on archeology and via literary sources from several isolated areas such as Ireland and Wales.