The gears of the Republic turn because of the Plebeians often referred to as "Plebs" or "Plebes" (pronounced Pleebs) and many of the higher classes recognize this knowing that they enjoy their elevated social status because of these people. Many newly arrived humans find their way into the Plebeian caste with ease while non-humans may have a more difficult time overcoming that hurdle. Most solve the issue by immediately enlisting in the military upon immigration to avoid spending any time in the Eeta caste.
Plebeians are allowed to vote, but cannot run for office. Many Great Houses will pander to the Plebeian caste around election time or during holiday celebrations to gain popular loyalty. The numbers of this caste make them powerful, however, they are not very organized relying mostly on patronage from the Nobilitas of the Great Houses to provide leadership and unity in times of difficulty or civil unrest. When the Plebs are happy, the people are happy and many Nobilitas recognize this fact of life.
Should a Plebeian prove themselves worthy through years of service, purchase an elevation of caste status, join a Ministry as an official or rise in rank high enough in the military they will advance to the Eques caste.