In tracing the history of Roman government, one would find that the first form of established rule was by that of the monarchy. This meant that one king held imperium over the mass of the people. However, by 510 B. C, with the elimination of the monarchy, this imperium was granted to two consuls who shared it equally, thus allowing for a new process of governing with division of power. The consuls held highly authoritative positions, dealing regularly with military and legal matters, and with general public affairs. As stated by Polybius, History of the World, 6.12. 1-9, "it is the duty of the consuls to consider these (public affairs) their concern, and to summon assemblies, to introduce resolutions, and to execute the decrees of the people".
Obviously, the consuls were faced with many major responsibilities, thus, the government was soon divided further to include magistracies. Only certain magistracies held imperium, besides the consuls, those being the praetors and the dictators. Praetors, described by the Historian Mess alla as "colleagues of the consuls", functioned in handling matters in the law, specifically that of civil law. Dictators were assigned to deal with affairs in times of urgency, such as war, and were entitled to power above all the other magistrates. This is emphasized in the following passage by Pomponius, The Digest of Laws, 1.2 16-28. : .".. occasionally, when the situation required, it was decided to establish a magistrate with power greater then any other magistrate. And thus dictators were appointed... to whom had been granted the power to inflict capital punishment.
Since this magistrate had absolute power, it was unconstitutional for him to be kept in office for more then six months". Though they did not hold imperium, other divisions of the government were also established, namely, the Quaestors, Tribunes of the plebs, Aedile's and Censors. Varro in A Book about the Latin Language, 5.14. 80-82, describes the derivation of these titles, and subsequently, the function of each in the governing of Rome: The censor was the one according to whose cen sio, that is "judgement" or "rating", the people should be censer i ["assesed,"rated"]. The aedile was the one who should look after sacred and private aedes ["buildings"]. The title quae stor was derived from quer ere ["to inquire"] since they are the ones who should inquire into the public finances...
The tribuni militum ["military tribunes"] were so called because long ago there were sent to the army three tribunes from each of the three tribus ["tribes"] The tribuni plebe i ["tribunes of the plebeians"] were so called because it was from the military tribunes that the tribunes of the plebians were first created, for the purpose of defending the plebians... The Aristocratic development of Rome becomes apparent when one studies the formation of the Comitia Centuriata, the Comitia Tributa and the Concilium Plebis. The Comitia Centuriata consisted of about 193 members, and "the people were fitted into the centurial in accordance with the amount of property they were registered... as holding". (Jones and Sidwell, The World of Rome, 114).
It is interesting to note that the people of this group voted according to division of class, so even though every person was said to be entitled to a vote, usually the votes of the wealthiest people formed majority, meaning that those of the lower classes often did not receive opportunity to vote. Voters of the Comitia Tributa were chosen according to their districts or localities, and were assemblies of the entire people. This unit originally consisted of four tribes in Rome, but eventually branched out to include citizens that did not live in the city. The Concilium Plebis was a group narrowed to the Plebs alone.
The Senate was a powerful unit in Rome. It consisted of 300 men appointed by the censors, and Senate members were all previous magistrates. Thus, the Senate had great influence over current magistrates and it was well respected. Senators were appointed for life and were very wealthy.
Performing the roles of "advisors", the Senate had authority over major decisions in governing Rome, and this is clear in the following passage by Cicero, In Defense of Plac ius, 65.137: "Our ancestors made the Senate the guardian, the leader and the defender of the state, and they want the magistrates to respect the authority of this order, and to be, so to speak, the servants of this most weighty position". While the first form of government in Rome was a monarchy, with one man having imperium over all the citizens, it is evident through the various forms of government that were eventually established in Rome that imperium would never again be limited to one individual or institution. This was partly ensured by the fact that all authoritative figures with imperium could hold office for only a limited time. The entitlement to vote by all the people of Rome allowed for a division of power among all the people, distributed highly to the authoritative figures, such as the Senators and Consuls, yet fairly down to the Tribunes, and created a mixed constitution in Rome. Thus, the absence of individual imperium was eliminated and to the benefit of all Rome's citizens.