The story of Western Christianities from Constantine to the close of the sixth century is one of both expansion and the formation of diverse Christianities. The themes that were in evidence across the Christian West throughout the period under consideration: political transformation and the formation of competing orthodoxies, the Christianisation of Western aristocracies, and the interplay between political and ecclesiastical structures. This chapter discusses the endorsement of bishops of the Nicene orthodoxy, the adherences of Roman Christianities by the provinces of Italy, Gaul, Spain and North Africa, to Nicene orthodoxy. As schisms within the churches of the Nicene tradition broke out after Chalcedon, the emperors and bishops of Constantinople faced the consequences. In the autumn of 482, Emperor Zeno addressed a letter to the Alexandrian church that proposed a compromise formula drafted by Acacius of Constantinople. Pope Vigilius had an aristocratic background and exemplified the trend towards the aristocratisation of the papacy.