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The Roman Senate was a political institution in ancient Rome. It was one of the most enduring institutions in Roman history, being established in the first days of the city (traditionally founded in 753 BC). It survived the overthrow of the kings in 509 BC, the fall of the Roman Republic in the 1st century BC, the division of the Roman Empire in 395 AD, the fall of the Western Roman Empire in 476 AD, and the barbarian rule of Rome in the 5th, 6th, and 7th centuries.
During the days of the kingdom, it was little more than an advisory council to the king. The last king of Rome, Lucius Tarquinius Superbus, was overthrown following a coup d'état led by Lucius Junius Brutus, who founded the Republic.
During the early Republic, the Senate was politically weak, while the executive magistrates were quite powerful. Since the transition from monarchy to constitutional rule was probably gradual, it took several generations before the Senate was able to assert itself over the executive magistrates. By the middle Republic, the Senate had reached the apex of its republican power. The late Republic saw a decline in the Senate's power, which began following the reforms of the tribunes Tiberius and Gaius Gracchus.
After the transition of the Republic into the Principate, the Senate lost much of its political power as well as its prestige. Following the constitutional reforms of the Emperor Diocletian, the Senate became politically irrelevant, and never regained the power that it had once held. When the seat of government was transferred out of Rome, the Senate was reduced to a municipal body. This decline in status was reinforced when the emperor Constantius II created an additional senate in Constantinople.
After the Western Roman Empire fell in 476, the Senate in the west functioned for a time under barbarian rule before being restored after the reconquest of much of the Western Roman Empire's territories during the reign of Justinian I. The Senate in Rome ultimately disappeared at some point between 603 and 630. However, the Eastern Senate survived in Constantinople, until the ancient institution finally vanished there with the capture of the city in 1204.
Senate of the Roman Kingdom
The senate was a political institution in the ancient Roman kingdom. The word senate derives from the Latin word senex, which means "old man"; the word thus means "assembly of elders". The prehistoric Indo-Europeans who settled Italy in the centuries before the legendary founding of Rome in 753 BC were structured into tribal communities, and these communities often included an aristocratic board of tribal elders.
The early Roman family was called a gens or "clan", and each clan was an aggregation of families under a common living male patriarch, called a pater (the Latin word for "father"). When the early Roman gentes were aggregating to form a common community, the patres from the leading clans were selected for the confederated board of elders that would become the Roman senate. Over time, the patres came to recognize the need for a single leader, and so they elected a king (rex), and vested in him their sovereign power. When the king died, that sovereign power naturally reverted to the patres.
The senate is said to have been created by Rome's first king, Romulus, initially consisting of 100 men. The descendants of those 100 men subsequently became the patrician class. Rome's fifth king, Lucius Tarquinius Priscus, chose a further 100 senators. They were chosen from the minor leading families, and were accordingly called the patres minorum gentium.
Rome's seventh and final king, Lucius Tarquinius Superbus, executed many of the leading men in the senate, and did not replace them, thereby diminishing their number. However, in 509 BC Rome's first consuls, Lucius Junius Brutus and Publius Valerius Publicola chose from amongst the leading equites new men for the senate, these being called conscripti, and thus increased the size of the senate to 300.
The senate of the Roman kingdom held three principal responsibilities: It functioned as the ultimate repository for the executive power, it served as the king's council, and it functioned as a legislative body in concert with the people of Rome. During the years of the monarchy, the senate's most important function was to elect new kings. While the king was technically elected by the people, it was actually the senate who chose each new king.
The period between the death of one king, and the election of a new king, was called the interregnum, during which time the Interrex nominated a candidate to replace the king. After the senate gave its initial approval to the nominee, he was then formally elected by the people, and then received the senate's final approval. At least one king, Servius Tullius, was elected by the senate alone, and not by the people.
The senate's most significant task, outside of regal elections, was to function as the king's council, and while the king could ignore any advice it offered, its growing prestige helped make the advice that it offered increasingly difficult to ignore. Technically, the senate could also make new laws, although it would be incorrect to view the senate's decrees as "legislation" in the modern sense. Only the king could decree new laws, although he often involved both the senate and the curiate assembly (the popular assembly) in the process.
Senate of the Roman Republic
When the Republic began, the Senate functioned as an advisory council. It consisted of 300 Senators, who were initially patrician and served for life. Before long, plebs were also admitted, although they were denied the senior magistracies for a longer period.
Senators were entitled to wear a tunic with a broad purple stripe, maroon shoes, and an iron (later gold) ring.
The Senate of the Roman Republic passed decrees called senatus consulta, which in form constituted "advice" from the senate to a magistrate. While these decrees did not hold legal force, they usually were obeyed in practice.
If a senatus consultum conflicted with a law (lex) that was passed by an assembly, the law overrode the senatus consultum because the senatus consultum had its authority based in precedent and not in law. A senatus consultum, however, could serve to interpret a law.
Through these advices, the senate directed the magistrates, especially the Roman consuls (the chief magistrates) in their prosecution of military conflicts. The senate also had an enormous degree of power over the civil government in Rome. This was especially the case with regards to its management of state finances, as only it could authorize the disbursal of public funds from the treasury. As the Roman Republic grew, the senate also supervised the administration of the provinces, which were governed by former consuls and praetors, in that it decided which magistrate should govern which province.
Since the 3rd century the senate also played a pivotal role in cases of emergency. It could call for the appointment of a dictator (a right resting with each consul with or without the senate's involvement). However, after 202, the office of dictator fell out of use (and was revived only two more times) and was replaced with the senatus consultum ultimum ("ultimate decree of the senate"), a senatorial decree which authorised the consuls to employ any means necessary to solve the crisis.
While senate meetings could take place either inside or outside of the formal boundary of the city (the pomerium), no meeting could take place more than a mile outside of it. The senate operated while under various religious restrictions. For example, before any meeting could begin, a sacrifice to the gods was made, and a search for divine omens (the auspices) was taken.
Meetings usually began at dawn, and a magistrate who wished to summon the senate had to issue a compulsory order. The senate meetings were public, and were directed by a presiding magistrate, usually a consul. While in session, the senate had the power to act on its own, and even against the will of the presiding magistrate if it wished. The presiding magistrate began each meeting with a speech, and then referred an issue to the senators, who would discuss the issue by order of seniority.
Senators had several other ways in which they could influence (or frustrate) a presiding magistrate. For example, all senators had to speak before a vote could be held, and since all meetings had to end by nightfall, a senator could talk a proposal to death (a filibuster or diem consumere) if he could keep the debate going until nightfall. When it was time to call a vote, the presiding magistrate could bring up whatever proposals he wished, and every vote was between a proposal and its negative.
At any point before a motion passed, the proposed motion could be vetoed, usually by a tribune. If there was no veto, and the matter was of minor importance, it could be voted on by a voice vote or by a show of hands. If there was no veto, and the matter was of a significant nature, there was usually a physical division of the house, with senators voting by taking a place on either side of the chamber.
Senate membership was controlled by the Censors. By the time of Gaius Marius, ownership of property worth at least one million sesterces was required for membership. The ethical requirements of senators were significant. In contrast to members of the Equestrian order, senators could not engage in banking or any form of public contract. They could not own a ship that was large enough to participate in foreign commerce, they could not leave Italy without permission from the senate and they were not paid a salary. Election to magisterial office resulted in automatic senate membership.
Senate of the Roman Empire
After the fall of the Roman Republic, the constitutional balance of power shifted from the Roman senate to the Roman emperor. Though retaining its legal position as under the republic, in practice, however, the actual authority of the imperial senate was negligible, as the emperor held the true power in the state. As such, membership in the senate became sought after by individuals seeking prestige and social standing, rather than actual authority.
During the reigns of the first emperors, legislative, judicial, and electoral powers were all transferred from the Roman assemblies to the senate. However, since the emperor held control over the senate, the senate acted as a vehicle through which he exercised his autocratic powers.
The first emperor, Augustus, reduced the size of the senate from 900 members to 600, even though there were only about 100 to 200 active senators at one time. After this point, the size of the senate was never again drastically altered. Under the empire, as was the case during the late republic, one could become a senator by being elected quaestor (a magistrate with financial duties), but only if one was of senatorial rank. In addition to quaestors, elected officials holding a range of senior positions were routinely granted senatorial rank by virtue of the offices that they held. 
If an individual was not of senatorial rank, there were two ways for him to become a senator. Under the first method, the emperor granted that individual the authority to stand for election to the quaestorship, while under the second method, the emperor appointed that individual to the senate by issuing a decree. Under the empire, the power that the emperor held over the senate was absolute.
During senate meetings, the emperor sat between the two consuls, and usually acted as the presiding officer. Senators of the early empire could ask extraneous questions or request that a certain action be taken by the senate. Higher ranking senators spoke before those of lower rank, although the emperor could speak at any time.
Besides the emperor, consuls and praetors could also preside over the senate. Since no senator could stand for election to a magisterial office without the emperor's approval, senators usually did not vote against bills that had been presented by the emperor. If a senator disapproved of a bill, he usually showed his disapproval by not attending the senate meeting on the day that the bill was to be voted on.
While the Roman assemblies continued to meet after the founding of the empire, their powers were all transferred to the senate, and so senatorial decrees (senatus consulta) acquired the full force of law. The legislative powers of the imperial senate were principally of a financial and an administrative nature, although the senate did retain a range of powers over the provinces.
During the early Roman Empire, all judicial powers that had been held by the Roman assemblies were also transferred to the senate. For example, the senate now held jurisdiction over criminal trials. In these cases, a consul presided, the senators constituted the jury, and the verdict was handed down in the form of a decree (senatus consultum), and, while a verdict could not be appealed, the emperor could pardon a convicted individual through a veto. The emperor Tiberius transferred all electoral powers from the assemblies to the senate, and, while theoretically the senate elected new magistrates, the approval of the emperor was always needed before an election could be finalized.
Around 300 AD, the emperor Diocletian enacted a series of constitutional reforms. In one such reform, he asserted the right of the emperor to take power without the theoretical consent of the senate, thus depriving the senate of its status as the ultimate depository of supreme power. Diocletian's reforms also ended whatever illusion had remained that the senate had independent legislative, judicial, or electoral powers. The senate did, however, retain its legislative powers over public games in Rome, and over the senatorial order.
The senate also retained the power to try treason cases, and to elect some magistrates, but only with the permission of the emperor. In the final years of the empire, the senate would sometimes try to appoint their own emperor, such as in the case of Eugenius, who was later defeated by forces loyal to Theodosius I. The senate remained the last stronghold of the traditional Roman religion in the face of the spreading Christianity, and several times attempted to facilitate the return of the Altar of Victory (first removed by Constantius II) to the senatorial curia.
Post-Imperial Senate in Rome
After the fall of the western Roman Empire, the senate continued to function under the barbarian chieftain Odoacer, and then under Ostrogothic rule. The authority of the senate rose considerably under barbarian leaders, who sought to protect the institution. This period was characterized by the rise of prominent Roman senatorial families, such as the Anicii, while the senate's leader, the princeps senatus, often served as the right hand of the barbarian leader. It is known that the senate successfully installed Laurentius as pope in 498, despite the fact that both King Theodoric and Emperor Anastasius supported the other candidate, Symmachus.
The peaceful coexistence of senatorial and barbarian rule continued until the Ostrogothic leader Theodahad began an uprising against Emperor Justinian I and took the senators as hostages. Several senators were executed in 552 as revenge for the death of the Ostrogothic king, Totila. After Rome was recaptured by the imperial (Byzantine) army, the senate was restored, but the institution (like classical Rome itself) had been mortally weakened by the long war. Many senators had been killed and many of those who had fled to the east chose to remain there, thanks to favorable legislation passed by Emperor Justinian, who, however, abolished virtually all senatorial offices in Italy. The importance of the Roman senate thus declined rapidly.
Relationships with Constantinople
In 578 and again in 580, the senate sent envoys to Constantinople. They delivered 3000 pounds (believed to be around 960 kg) of gold as a gift to the new emperor, Tiberius II Constantinus, along with a plea for help against the Lombards, who had invaded Italy ten years earlier. Pope Gregory I, in a sermon from 593, lamented the almost complete disappearance of the senatorial order and the decline of the prestigious institution.  
It is not clearly known when the Roman senate disappeared in the West, but it is known from the Gregorian register that the senate acclaimed new statues of Emperor Phocas and Empress Leontia in 603. The institution is assumed to have vanished by 630 when the Curia Julia was transformed into a church by Pope Honorius I.
In later medieval times, the title "senator" was still in occasional use, but it had become a meaningless adjunct title of nobility and no longer implied membership in an organized governing body.
In 1144, the Commune of Rome attempted to establish a government modeled on the old Roman republic in opposition to the temporal power of the higher nobles and the pope. This included setting up a senate along the lines of the ancient one. The revolutionaries divided Rome into fourteen regions, each electing four senators for a total of 56 (though one source,[which?] often repeated, gives a total of 50). These senators, the first real senators since the 7th century, elected as their leader, Giordano Pierleoni, son of the Roman consul Pier Leoni, with the title patrician, because consul was also a deprecated noble styling.
This renovated form of government was constantly embattled. By the end of the 12th century, it had undergone a radical transformation, with the reduction of the number of senators to a single one - Summus Senator - being thereafter the title of the head of the civil government of Rome. (For example, in modern terms, this is comparable to the reduction of a board of commissioners to a single commissioner, such as the political head of the police department of New York City.) Between 1191 and 1193, this was a certain Benedetto called Carus homo or carissimo.
Senate of the Eastern Roman Empire
The senate continued to exist in Constantinople, however. In the second half of the 10th century a new office, proëdrus (Greek: πρόεδρος), was created as head of the senate by Emperor Nicephorus Phocas. Up to the mid-11th century, only eunuchs could become proëdrus, but later this restriction was lifted and several proëdri could be appointed, of which the senior proëdrus, or protoproëdrus (Greek: πρωτοπρόεδρος), served as the head of the senate. There were two types of meetings practised: silentium, in which only magistrates currently in office participated and conventus, in which all syncletics (Greek: συγκλητικόι, senators) could participate. The senate in Constantinople existed at least until the beginning of the 13th century, its last known act being the election of Nicolas Canabus as emperor in 1204 during the Fourth Crusade.
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