This study attempts to put into its correct historical context the single surviving page of a tract entitled De fide. The work was written by a certain "Agrestius" and dedicated to a certain "Avitus." In this study, Agrestius is identified as the bishop Agrestius of Lugo (in the Spanish province of Galicia) who attended the Gallic Council of Orange in the year 441. Avitus is identified as Eparchius Avitus, known to have been praetorian prefect of Gaul in 439, then emperor in 455-56.
It is suggested that Agrestius of Lugo sought assistance in Gaul because of factional quarreling in Galicia. Because this quarreling involved accusations of heresy (Priscillianism), Agrestius had to attest to his orthodoxy when he visited Gaul—the De fide was part of this process. But the quarreling also resulted from questions of authority in Galicia—it seems that bishops such as Syagrius and Pastor, two of Agrestius' rivals, were being ordained in out-of-the-way places by various factions. Some of these quarrels also seem to have been the result of questions of jurisdiction involving the continued use in Spain of the old conventus, or judicial district.
In Gaul, the episcopal establishment welcomed Agrestius' visit because it allowed Hilary of Aries and his partisans to have the appearance of extending their authority into Spain. The secular establishment, meanwhile, represented by Avitus, was happy to cooperate by placing its imprimatur upon Agrestius' orthodoxy. Eventually, however, the bishop of Rome, Leo, undertook to extend his authority into both Gaul and Spain. In 445, Leo issued rulings contrary to Hilary in Gaul, and in 447 he seems to have sided with Agrestius' rivals in Spain. The opportunity for a measure of unity among the western European churches represented by Agrestius' initiative in Gaul, therefore, eventually came to nought.