The letters of Avitus are of considerable importance for the ecclesiastical and political history of the years between 499 and 518. Like his contemporary, Ennodius of Pavia, he was strenuous in his assertion of the authority of the Apostolic See as the chief bulwark of religious unity and the incipient Christian civilization. "If the pope," he says, "is rejected, it follows that not one bishop, the whole episcopate threatens to fall" (Si papa urbis vocatur in dubium, episcopatus videbitur, non episcopus, vaccilare. — Ep. xxxiv; ed. Peiper). His letters are also among the important primary sources of early Merovingian political, ecclesiastical, and social history. Among them is a famous letter to Clovis on the occasion of his baptism. Avitus addresses Clovis not as if he was a pagan convert, but as if he was a recent Arian sympathiser, possibly even a catechumen. The letters document the close relations between the Catholic Bishop of Vienne and the Arian king of the Burgundians, the great Gundobad, and his son, the Catholic convert Sigismund.