- Its foundation and development
The Republic declined, largely because it was unable to solve its administrative problems which had increased following Rome's expansion. Octavianus (known after 27 B.C. as Augustus) restored the order which was threatening to vanish in civil war. Under the cloak of bringing back the Republican constitution the nominally shared power with the Senate but, in fact, ruled as a monarch.
The Period from 27 B.C. is known as the Principate (princeps = first citizen). From Diocletian (A.D. 284) an absolute monarchy was in existence and that period is known as the Dominate (dominus = master). The Empire was divided for purposes of administration in A.D. 364, when Valentinian II and Valens became joint Emperors. Rome was sacked in A.D. 410 and in A.D. 455. The Western Empire collapsed in the late fifth century, but the Eastern Empire survived and continued, nominally, until the fifteenth century. Justinian ruled as Emperor of the East from A.D. 527-565.
- Changes in the legal system
+ The Senate
Senatusconsulta became, after the early days of the Empire, a mere expression of the imperial will. The independence of the Senate declined and its powers withered away. Thus, in A.D. 282, following the murder of the Emperor Probus, a new Emperor, Carus, was elected by the military and ascended the throne without the preliminary authority of the Senate. The Emperor's power, based on his army, was henceforth the real source of legislative authority.
