In a monarchy, which, according to various precedents, might be considered as elective, or hereditary, or patrimonial, it was impossible that the intricate claims of female and collateral succession should be clearly defined; and Theodosius, by the right of consanguinity or conquest, might have reigned the sole legitimate emperor of the Romans. For a moment, perhaps, his eyes were dazzled by the prospect of unbounded sway; but his indolent temper gradually acquiesced in the dictates of sound policy. He contented himself with the possession of the East; and wisely relinquished the laborious task of waging a distant and doubtful war against the Barbarians beyond the Alps; or of securing the obedience of the Italians and Africans, whose minds were alienated by the irreconcilable difference of language and interest. Instead of listening to the voice of ambition, Theodosius resolved to imitate the moderation of his grandfather, and to seat his cousin Valentinian on the throne of the West. The royal infant was distinguished at Constantinople by the title of Nobilissimus: he was promoted, before his departure from Thessalonica, to the rank and dignity of Cæsar; and after the conquest of Italy, the patrician Helion, by the authority of Theodosius, and in the presence of the senate, saluted Valentinian the Third by the name of Augustus, and solemnly invested him with the diadem and the Imperial purple. By the agreement of the three females who governed the Roman world, the son of Placidia was betrothed to Eudoxia, the daughter of Theodosius and Athenais; and as soon as the lover and his bride had attained the age of puberty, this honorable alliance was faithfully accomplished. At the same time, as a compensation, perhaps, for the expenses of the war, the Western Illyricum was detached from the Italian dominions, and yielded to the throne of Constantinople. The emperor of the East acquired the useful dominion of the rich and maritime province of Dalmatia, and the dangerous sovereignty of Pannonia and Noricum, which had been filled and ravaged above twenty years by a promiscuous crowd of Huns, Ostrogoths, Vandals, and Bavarians. Theodosius and Valentinian continued to respect the obligations of their public and domestic alliance; but the unity of the Roman government was finally dissolved. By a positive declaration, the validity of all future laws was limited to the dominions of their peculiar author; unless he should think proper to communicate them, subscribed with his own hand, for the approbation of his independent colleague.