MAGISTER OFFICIORUM. – He is one of the great central officials of the absolute Roman Empire, that is, of the form it assumed following the Diocletian-Constantinian constitutional reform.
His name is probably due to the fact that he directed the officia or scrimia, that is, the sections of the imperial chancery. But the functions entrusted to him are so numerous and extend over such different fields that it is difficult to define his office in modern terms. Toward the end of the fourth century he already belonged to the highest category of imperial officials, that of the illustres.
The m. o. commands the scholae palatinae, an armed corps that took the place of the disbanded praetorian cohorts; the schola of the agentes in rebus publicis, who are entrusted with supervisory duties in matters relating to public administration; he directs the imperial postal service and that of those responsible for preparing accommodations for the emperor and his retinue on their journeys.
The arms factories are subject to the supervision of the m. o. The officium admissionum, which regulates imperial audiences, is placed under his authority; he is therefore responsible for maintaining relations with representatives of the cities of the Empire and of foreign states, which enables him to influence foreign policy.
He is also vested with civil and criminal jurisdiction over all court personnel and, in connection with the oversight he exercises over the frontiers of the Empire, with jurisdiction over the frontier troops and their commanders.