This paper begins from the Epistle 121 of Synesius, the bishop of Ptolemais. It reveals a high sense of state and a full acceptance of the role of bishop also in the imposition of civil justice (“holy public office”). The writings of the same period by other bishops (the Oriental-Greek bishops as much as those of the West, from Gregory of Nazianzus to Maximus of Turin) confirm this willingness to be part of an imperial power, remote but at the same time operative through local authorities which the bishop was able and indeed obliged to monitor closely. It is shown how the absence of any conflict between the conscience of the priest and that of the imperial official finds its most explicit formulations in Ambrose of Milan, whose relationships with the highest ranks of political power (often present in the city) were, however, much closer and more complex. In response to recent studies (N. McLynn) an attempt has been made through a precise analysis of sources and specific situations to show how it was this self-same ex-clarissimus Ambrose who elaborated a new episcopal style able to safeguard and increase the prestige of his own authority also of a secular nature thanks to a charismatic “shield” patiently constructed and carefully dispensed in its formulations and the scriptural models selected: in particular, the exemplum of the prophet Elisha, the king's counsellor and the worker of countless miracles to guarantee his own authority (Elisha, once the favourite of Athanasius of Alexandria whom Ambrose must have met in Rome in his youth and whose follower he became both in theology and sometimes in literature). Thus on the foundation of this new “rhetoric” of episcopal power, on an unremitting pastoral and exegetic activity and on the attentive choice of collaborators of an elevated cultural level within his own sphere of influence Ambrose set in motion an episcopal model of high profile. In Northern Italy as in Gaul this model can be discerned sustaining the “noble bishops” of the 5th and 6th century, who become more and more rigidly distinct from the mass of the faithful and revered for their political as much as for their spiritual virtues. This was a radical mutation within the ecclesiastical ranks and is quite unparalleled in the dioceses of peninsular Italy of that time. [Author]