Principate
The Principate was the early period of the Roman Empire, and it began with a performance. On the 13th of January 27 BC, the man who had just won Rome's civil wars walked into the Senate chamber and offered to give everything back. Octavian declared he was returning full power to the Senate and relinquishing his control of the provinces and their armies. Three days later, on the 16th of January, the Senate voted to give it all back to him anyway, along with a new title: augustus, a name carrying religious rather than political weight, one that edged its holder toward the divine.
This sleight of hand was not an accident. It was the founding gesture of a system built on the appearance of republican tradition while concentrating power in a single man. The word for that system comes from the Latin princeps, meaning 'leading citizen' or 'first citizen', a title that had once been spread among Roman nobles and was now focused entirely on one person.
How did Octavian build this position step by step? How did later emperors transform, expand, and sometimes crack the architecture he created? And what did 19th-century scholars make of the whole arrangement centuries later, in ways that shaped how historians still argue about Rome today?
During the Roman Republic, the princeps senatus was the most influential member of the Senate, a position Sulla abolished and Augustus revived in 28 BC. The title carried precedence: the princeps senatus spoke first, set the tone, and commanded the room's attention without formally outranking anyone.
Octavian took that older, distributed concept of a 'first among equals' and quietly narrowed it to a single point. Scholars had previously applied the word princeps to any Roman noble who distinguished themselves in service to the Republic. By embracing it, Octavian presented himself not as a monarch or a dictator but as a restoration figure, someone who had returned to the old ways.
In the 19th century, the German scholar Theodor Mommsen gave this arrangement its scholarly name. The historian Jochen Bleicken credits Mommsen with introducing the constitutional concepts of 'Principate' and 'Dominate' as a framework for breaking Roman imperial history into periods. Mommsen saw the Principate as a kind of diarchy, a formal power-sharing between Augustus as princeps and the Senate. He viewed it as an extension of the Republic, one that held together until the 3rd century, when it collapsed into the more openly autocratic Dominate under Diocletian.
That interpretation did not survive long into the 20th century. Historians following Ronald Syme began calling the Principate a variant of monarchy, and scholars have since moved through several frameworks: networks of people in the 1910s-1930s, ruler-community interaction in the 1960s to mid-1980s, and now approaches shaped by the social and political sciences. By the 21st century, 'Augustan Age' had become the more common framing for the foundational period.
In August 29 BC, Octavian received three triumphs in Rome for victories in Illyria, Greece, and Egypt. The celebrations marked not just military success but the symbolic end of the civil wars and the beginning of his careful accumulation of authority.
He and his ally Agrippa were elected consuls for 28 BC. That year they were also granted certain powers of the censor without holding the office itself, specifically for conducting Rome's census. The distinction mattered: Octavian consistently gathered powers while avoiding the titles that would make his position look like a monarchy.
The settlement of the 16th of January 27 BC gave him a ten-year responsibility over provinces considered chaotic, which in practice meant command over the majority of Rome's legions. The Senate retained nominal control over other provinces, lending the arrangement a republican appearance. But Augustus's imperium maius let him issue instructions even to governors of those nominally independent provinces.
By 23 BC, complications had appeared. After dealing with a severe illness, Augustus gave up his consulship on the 1st of July of that year, but he wanted to keep his consular authority across the whole empire. The 'Marcus Primus affair', which was seen as a breach of the Senate's rights under the 27 BC settlement, helped prompt a second compromise. The Senate granted Augustus imperium proconsulare maius, a form of authority superior to all other proconsuls and valid throughout the empire. He also received tribunicia potestas, the power of a tribune, for life. This let him convene the Senate, veto decisions by the Assembly or Senate, preside over elections, and speak first at any meeting.
On the 6th of March 12 BC, following the death of Lepidus, Augustus took on the role of pontifex maximus, the most eminent position in Roman religion. Every emperor after him held that title until the fall of the Western Roman Empire in AD 476, at which point the papacy in Rome adopted it.
Historians Werner Eck and Sarolta Takacs identified three pillars of Augustus's authority: powers delegated by the Senate and people, his immense private fortune, and the patron-client relationships he built across the empire. All three fed what Augustus himself called his auctoritas, the personal authority he named as the foundation of his political actions.
The conquest of Ptolemaic Egypt was decisive for the financial side. It cleared the debts Augustus had accumulated during the civil wars, and afterward he kept direct control over Roman Egypt, barring senators from traveling there entirely. Egypt's taxation was highly lucrative, and its revenues underwrote everything that followed.
Patronage in ancient Rome was an exchange relationship between people of unequal status and resources, and during the Principate scholars see it as central to social order. Augustus was described as the 'ultimate source of patronage', using it to build loyalty and a shared identity across a vast empire. He was given the title pater patriae, 'father of the country', inscribed in places including the Senate chambers in the Forum Romanum. In Roman culture the father as head of the household held the highest regard, and Augustus appears to have preferred pater to patronus as a description of his role.
Military loyalty followed similar logic. Augustus split management of the provinces with the Senate, presenting the arrangement as administrative practicality. But he retained the loyalty of active soldiers and veterans regardless of who formally commanded any given region, and he ultimately institutionalised command of the military as a feature of the Principate itself.
Tiberius, who followed Augustus, was careful to present himself as a servant of the Senate rather than its master. He offered a definition of the ideal princeps: one 'whom you have invested with such great discretionary power, ought to be the servant of the Senate, and often of the whole citizen body'. Yet the distance between that rhetoric and political reality kept widening.
As Dio Cassius recorded, Caligula 'took in one day all the honours which Augustus had with difficulty been induced to accept'. The careful, incremental accumulation that had defined the Augustan model gave way to something more direct.
The political reality underneath the Principate's surface was autocratic rule, but it was masked by the forms and conventions of oligarchic self-rule inherited from the Republic that had run from 509 BC to 27 BC. The motto Senatus Populusque Romanus, 'The Senate and people of Rome', or SPQR, remained the official framing. Imperial propaganda presented the princeps as the embodiment of virtues expected of an ideal ruler: clemency, justice, military leadership. This created obligations. Tiberius, who accumulated a large surplus for the city of Rome, was criticised as a miser. His successor Caligula was criticised for spending lavishly on games and spectacles. The role demanded generosity without excess, a balance the proverbial 'bread and circuses', panem et circenses, tried to strike through public games, gladiators, chariot races, food distributions, and public works.
With the fall of the Julio-Claudian dynasty in AD 68, the position of princeps became a distinct legal entity. Vespasian, who came to power from AD 69, established a legal basis for succession by listing the offices and powers he had inherited from Augustus, Tiberius, and Claudius in the lex quae dicitur de imperio Vespasiani. Rule was no longer even notionally granted on merit or auctoritas; it rested on a firmer legal footing that let emperors designate their own heirs.
Under the Antonine dynasty it became standard for emperors to appoint a capable and politically promising individual as their successor. Later scholars often held this up as the ideal arrangement, with the position of princeps passing on ability rather than birth. Modern scholarship has generally rejected the idea that this was the emperors' own intention.
The reign of Marcus Aurelius produced the first formally recognised co-rule in Roman imperial history. Marcus Aurelius and Lucius Verus ruled jointly from their accession in 161 AD until Lucius Verus died in 169 AD.
When Commodus succeeded Marcus Aurelius, he became the first emperor's son born during a father's reign to inherit the position. He is often ranked among the worst Roman emperors, and his 12-year reign ended in civil war between rival generals. The Severan dynasty that followed was the final dynasty of the Principate, and the absence of any explicit succession law in Roman legal tradition left the empire exposed each time a ruling house collapsed.
The Crisis of the Third Century marks the conventional close of the Principate. What came after, the Dominate under Diocletian, was the rupture Mommsen had identified, a more openly autocratic system that no longer bothered with the republican forms the princeps had so carefully maintained for three centuries.
Common questions
What was the Roman Principate and when did it begin?
The Principate was the early period of the Roman Empire, beginning with Augustus's reign as the first Roman emperor in 27 BC. It conventionally lasted until the late third century, often linked to the Crisis of the Third Century, after which the Dominate began under Diocletian.
What does the word princeps mean in the context of the Roman Principate?
Princeps means 'leading citizen' or 'first citizen' in Latin. The title had previously been applied to Roman nobles who distinguished themselves in service to the Republic; Augustus refashioned it as the title for the sole ruler of Rome, while preserving its republican connotation.
How did Augustus gradually gain power during the Principate?
Augustus accumulated power incrementally through a series of settlements with the Senate. On the 16th of January 27 BC, the Senate granted him oversight of Rome's most turbulent provinces and their legions. By 23 BC he had also received imperium proconsulare maius, authority superior to all other proconsuls across the whole empire, and tribunicia potestas for life. On the 6th of March 12 BC he became pontifex maximus.
Who was Theodor Mommsen and what did he argue about the Roman Principate?
Theodor Mommsen was a 19th-century German scholar who introduced the constitutional concepts of 'Principate' and 'Dominate' as a framework for Roman imperial history. He viewed the Principate as a diarchy in which power was formally shared between Augustus and the Senate from 27 BC, and considered it an extension of the Republic until its rupture in the 3rd century. Later historians, following Ronald Syme, rejected this view and called the Principate a variant of monarchy.
How did succession work during the Roman Principate?
Roman law contained no explicit outline for how emperors should be chosen or who could become princeps. Augustus based succession on auctoritas, personal authority earned by merit. After the fall of the Julio-Claudian dynasty in AD 68, Vespasian established a firmer legal basis via the lex quae dicitur de imperio Vespasiani. Under the Antonine dynasty, emperors typically appointed a capable successor, but modern scholarship rejects the idea this was a deliberate policy. Commodus, whose 12-year reign began after Marcus Aurelius, was the first emperor's son born during a father's reign to inherit the position.
When did the Roman Principate end and what replaced it?
The Principate conventionally ended with the Crisis of the Third Century in the late third century AD. It was replaced by the Dominate, a more overtly autocratic system associated with the reign of Diocletian, which Mommsen had identified as the rupture breaking the Principate's republican forms.
All sources
3 references cited across the entry
- 1JournalPrincipateDec 22, 2015
- 2JournalSecond Thoughts on the Imperial Succession from Nerva to CommodusRussel Mortimer Geer — 1936
- 3BookThe Roman Imperial SuccessionJohn D. Grainger — Pen and Sword History — 30 June 2020