While individual plebeians, or freeborn Roman citizens outside the patrician, senatorial and equestrian classes, were able to gain economic power by amassing wealth and joining the equestrian class, their chances of joining the politically influential senatorial class were extremely remote. Collectively, however, plebeians were able to effect political and social change by forming a mob and rebelling against their social superiors.
I am not so sure about tge 2nd part
