An early mention of Christmas observance is from 129 AD when a Roman bishop decreed: "In the Holy Night of the Nativity of our Lord and Saviour, all shall solemnly sing the Angels Hymn." In 274 AD, Emperor Aurelian made a festival for Sol Invictus ("The Unconquered Sun"), originally a Syrian deity who was later adopted as the chief deity of the Roman Empire. While some writers believe this may have influenced the Christian feast of Christmas, other historians such as Louis Duchesne, and Thomas Talley maintain that the Christian feast of Christmas was already being celebrated and that Aurelian established "Dies Natalis Solis Invicti" in order to compete with the Christian feast of Christmas.