IT is natural to think of Diocletian as the projector and of Constantine as the completer of a new system of government for the Roman Empire, which persisted with mere changes of detail until it was laid in ruins by the barbarians. But in reality the imperial institutions from the time of Augustus onwards had passed through a course of continuous development. Diocletian did but accelerate processes which had been in operation from the Empire’s earliest days, and Constantine left much for his successors to accomplish. Still these two great organizers did so far change the world which they ruled as to be rightly styled the founders of a new type of monarchy. We will first sketch rapidly the most striking aspects of this altered world, and then consider them one by one somewhat more closely. But our survey must be in the main of a general character, and many details, especially when open to doubt, must be passed over. In particular, the minutiae of chronology, which in this region of history are specially difficult to determine, must often be disregarded.

The ideal of a balance of power between the Princeps and the Senate, which Augustus dangled before the eyes of his contemporaries, was never approached in practice. From the first the imperial constitution bore within it the seed of autocracy, and the plant was not of slow growth. The historian Tacitus was not far wrong when he described Augustus as having drawn to himself all the functions which in the Republic had belonged to magistrates and to laws.

The founder of the Empire had studied well the art of concealing his political art, but the pressure of his hand was felt in every corner of the administration. Each Princeps was as far above law as he chose to rise, so long as he did not strain the endurance of the Senate and people to the point of breaking. When that point was passed there was the poor consolation of refusing him his apotheosis, or of branding with infamy his memory. As the possibility of imperial interference was ever present in every section of the vast machine of government, all concerned in its working were anxious to secure themselves by obtaining an order from above. This anxiety is conspicuous in the letters written by Pliny to his master Trajan. Even those emperors who were most citizen-like (civiles as the phrase went) were carried away by the tide. Tacitus exhibits the Senate as eagerly pressing Tiberius to permit the enlargement of his powers—Tiberius who regarded every precept of Augustus as a law for himself. The so-called lex regia Vespasiani shows how constantly the admitted authority of the emperor advanced by the accumulation of precedents. Pliny gave Trajan credit for having reconciled the Empire with ‘liberty’; but ‘liberty’ had come to mean little more than orderly and benevolent administration, free from cruel caprice, with some external deference paid to the Senate. Developed custom made the rule of Marcus Aurelius greatly more despotic than that of Augustus. Even the emperors of the third century who, like Severus Alexander, made most of the Senate, could not turn back the current. It was long, however, before the subjects of the Empire realized that the ancient glory had departed. Down to the time of the Emperor Tacitus (275-276 AD) pretenders found their account in posing as senatorial champions, and rulers used the Senate’s name as a convenient screen for their crimes.

Diocletian

But the natural outcome of the anarchy of the third century was the unveiled despotism of Diocletian. He was the last in a line of valiant soldiers sprung from Illyrian soil, who accomplished the rescue of Rome from the dissolution with which it had been threatened by forces without and by forces within. To him more than to Aurelian, on whom it was bestowed, belonged by right the title “restorer of the world.” For three centuries the legions had been a standing menace to the very existence of Greco-Roman civilization. They made emperors and unmade them, and devoured the substance of the State, exacting continually lavish largess at the sword’s point. One hope of Diocletian when, following in the steps of Aurelian, he hedged round the throne with pomp and majesty, was that a new awe might shield the civil power from the lawless soldiery. In place of an Augustus, loving to parade as a bourgeois leader of the people, there comes a kind of Sultan, with trappings such as the men of the West had been used to associate with the servile East, with the Persians and Parthians. The ruler of the Roman world wears the oriental diadem, the mere dread of which had brought Caesar to his end. He is approached as a living god with that adoration from which the souls of the Greeks revolted when they came into the presence of the Great King, though Alexander bent them to endure it. Eunuchs are among his greatest officers. Lawyers buttress his throne with an absolutist theory of the constitution which is universally accepted.

The growth of Centralization

From Augustus to Diocletian the trend of the government towards centralization had been incessant. The new monarchy gave to the centralization an intensity and an elaboration unknown before. In the early days of conquest, whether within Italy or beyond its boundaries, the Roman power had attempted no unification of its dominions. As rulers, the Romans had shown themselves thorough opportunists. They tolerated great varieties of local privilege and partial liberty. Their government had followed, almost timidly, the line of least resistance, and had adapted itself to circumstance, to usage, and to prejudice in every part of the Empire. Even taxation had been elastic. Before the age of despotism, few matters had ever been regulated by one unvarying enactment for every province. To this great policy the Romans chiefly owed the rapidity of their successes and the security of their ascendancy.

Caracalla

The tendency towards unity was of course manifest from the first. But it sprang far less from the direct action of the central government than from the instinctive and unparalleled attraction which the Roman institutions possessed for the provincials, particularly in the West. In part by the extension of Roman and Italian rights to the provinces, in part by the gradual depression of Italy to the level of a province, and in part by interference designed to correct misgovernment, local differences were to a great extent effaced. Septimius Severus (145-211 AD) by stationing a legion in Italy removed one chief distinction between that favored land and the subject regions outside. Under his successor, Caracalla (211-217 AD), all communities within the Empire became alike Roman. By Diocletian and by Constantine, control from the centre was made systematic and organic. Yet absolute uniformity was not attained. In taxation, in legal administration, and in some other departments of government, local conditions still induced some toleration of diversities.

Centralization brought into existence with its growth a vast bureaucracy. The organization of the Imperial side of the administration, as opposed to the Senatorial, became more and more complex, while the importance of the Senate in the administrative machinery continually lessened. The expansion and organization of the executive engaged the attention of many emperors, particularly Claudius, Vespasian, Trajan, Hadrian, and Septimius Severus. When the chaos of the third century had been overcome, Diocletian and his successors were compelled to reconstruct the whole service of the Empire, and a great network of officials, bearing for the most part new titles and largely undertaking new functions, was spread over it.

Along with the development of absolutism and the extension of bureaucracy, and the unification of administration had gone certain tendencies which had cut deeply into the constitution of society at large. The boundaries between class and class tended more and more to become fixed and impassable. As the Empire decayed society stiffened, and some approximations were made to the oriental institution of caste. Augustus had tried to give a rigid organization to the circle from which senators were drawn, and had constituted it as an order of nobility passing down from father to son, only to be slowly recruited by imperial choice. Many duties owed to the State tended to become hereditary, and it was made difficult for men to rid themselves of the status which they acquired at birth. The exigencies of finance made membership of the local senates in the municipalities almost impossible to escape.

The frontier legions, partly by encouragement and partly by ordinance, were largely filled with sons of the camp. Several causes, the chief of which was the financial system, gave rise to a kind of serfdom (colonatus) which at first attached the cultivators of the soil, and as time went on, approximated to a condition of actual slavery. The provisioning of the great capitals, Rome and Constantinople, and the transportation of goods on public account, rendered occupations connected with them hereditary. And many inequalities between classes became pronounced. The criminal law placed the honestiores and the tenuiores in different categories.

The new form of the Executive Government 

The main features of the executive government as organized by Diocletian and his successors, must now be briefly...