How Did the Roman Senate Work?

The Roman Senate — the Senatus Populusque Romanus, the “Senate and People of Rome” — was the most durable and influential governing institution of the ancient world. From the founding of the Republic in 509 BCE to the fall of the Western Empire in 476 CE, the Senate was the principal council of the Roman state, advising the magistrates, controlling the public finances, directing the foreign policy of the Republic, and in the imperial period providing the administrative backbone of the empire. For the broader context, see the complete history of the Roman Empire.

The Senate was not a parliament in the modern sense. It could not pass laws on its own; laws were passed by the popular assemblies. It could not, except in a state of emergency, command armies or exercise judicial power on its own. What the Senate could do, and what it did with great effect for almost a thousand years, was to give formal advice — senatus consulta, “the Senate’s considered opinions” — to the magistrates of Rome, and to set the political agenda of the state. The magistrates, who were the elected executives of the Republic, were expected to follow the Senate’s advice, and the Senate’s prestige was such that they almost always did.

The Members of the Senate

The early Senate was a council of elders drawn from the patrician families. The Roman tradition, recorded by Livy and Cicero, held that the Senate was originally appointed by Romulus, the legendary founder of Rome, and reorganized in the 5th century BCE by the kings Tarquinius Priscus and Servius Tullius into a body of 300 members.

In the early Republic, the Senate was drawn exclusively from the patricians, but after the Conflict of the Orders (494–287 BCE) the plebeians were gradually admitted. By the 2nd century BCE the Senate was a body of about 300 men, all of them former magistrates. For the political history of this period, see the Roman Republic.

The size of the Senate grew over time. The dictator Sulla raised the number to 600 in 81 BCE; Julius Caesar raised it to 900. Augustus set the number at 600 in 28 BCE, and this remained the standard for the imperial period.

A senator had to be a Roman citizen, of good character, and of sufficient wealth. The minimum census qualification was 1,000,000 sesterces — a substantial fortune.

The Princeps Senatus

The most senior member of the Senate held the title princeps senatus, the “first man of the Senate.” In the Republic, the princeps senatus was the senator whose name appeared first on the senatorial roll, and he was entitled to speak first in any debate. The office was held for life.

In the imperial period, the title of princeps senatus was held by the emperor himself, and it was one of the many republican forms that Augustus carefully preserved to mask the new realities of imperial power. The emperor was the first senator, the leading member of the senatorial class, and the rest of the senators were technically his peers — a fiction that was carefully maintained for the next three centuries. For Augustus, see Augustus Caesar.

Meetings of the Senate

The Senate met in a number of different buildings over the centuries. The earliest meeting place was the Curia Hostilia, named after the legendary third king Tullus Hostilius, and rebuilt in stone in the 80s BCE. The Curia was replaced by the Curia Julia, begun by Caesar and completed by Augustus, which still stands in the Roman Forum. For the setting, see What Was the Roman Forum?.

The Senate could meet in two ways: a senatus consultum “on a stated day,” called by a magistrate at least three days in advance, and a senatus consultum “on an immediate matter,” called in an emergency. The emperor, in the imperial period, had the right to call the Senate and to set the agenda through a written communication called a relatio. The Senate would issue a senatus consultum — a formal opinion — which the emperor could accept, modify, or reject.

The Powers of the Senate

The Senate’s powers in the Republic were enormous, even though it could not directly legislate. It controlled the public finances of the state, including the treasury, the mint, and the taxes. It directed the foreign policy of the Republic: it decided on the allocation of military commands, the treaties with foreign powers, the reception of foreign embassies, and the awarding of triumphs. It advised the consuls on the conduct of war, and it could, in a crisis, appoint a dictator — a temporary ruler with absolute power.

In the judicial sphere, the Senate acted as a court of last resort, especially in cases of treason (maiestas). The censors, who were senators, were responsible for the composition of the senatorial and equestrian orders.

The Decline of the Senate

The Senate’s powers began to decline in the late Republic, as the great generals — Marius, Sulla, Pompey, Caesar — accumulated military power and used it to override the Senate. The decisive moment came in 49 BCE, when Caesar crossed the Rubicon with his army and marched on Rome. For this long collapse, see the fall of the Roman Republic.

Augustus, who defeated Caesar’s assassins and became the first emperor in 27 BCE, was careful to preserve the forms of the Republic while concentrating real power in his own hands. The Senate continued to meet and to issue senatus consulta, but the real decisions were made by the emperor. The Senate became the municipal council of the city of Rome.

The Senate did retain some real powers under the empire. It still controlled the administration of the city of Rome, including the grain supply, the public works, and the games. It still acted as a court of law for senators.

By the 3rd century CE the Senate had been reduced to a purely ceremonial body. The emperor Diocletian (r. 284–305 CE) abolished the old senatorial career and replaced it with a new imperial bureaucracy. For Diocletian’s reforms, see Diocletian and the Tetrarchy.

The Senate Under the Late Empire

Constantine the Great (r. 306–337 CE) reorganized the Senate in 318 CE, separating the senatorial order from the equestrian order. Constantine also created a second Senate, in the new imperial capital of Constantinople, which he founded in 330 CE. The two Senates coexisted for centuries, and the Senate of Constantinople survived the fall of the Western Empire in 476 CE. For Constantine, see Constantine the Great.

The Senate of Rome itself was abolished in 580 CE, when the last Roman Senate was dissolved by the Lombard invasion. The Senate had lasted, in one form or another, for nearly a thousand years — one of the longest-lived political institutions in history.