This question causes us some trouble at the outset. The ancients of course did not know the term “middle class”, which does not mean that there was no social group situated between the social elite and the urban poor. However, its definition is not easy.
The Romans themselves would probably consider the middle-class equites, an intermediate state between the senatorial aristocracy (nobilitas) and the plebs. The problem is that from the third century BCE the property certificate for this group was 400,000 sesterce – quite a lot. In the time of Marius (turn of the 2nd and 1st century BCE), the annual legionary’s pay was 1,200 sesterce, and when 50 years later it was doubled by Caesar, only 2400. The Roman equit, therefore, had to have a property equivalent to 4000 (later 2000) monthly wages in a legionary’s line. Translating our approximate calculations into modern realities, the equites had really large assets – remember that the census is the minimum amount – in practice, most representatives of this class were much richer. To sum up – it would be difficult for us to call a multimillionaire a representative of the middle class…
If, in turn, we consider working intelligence as the middle class, we may have a different problem. The Roman administration was not particularly extensive. In fact, until the time of Octavian Augustus there was practically no civil administration in the provinces – the Romans left everything to conquered peoples, and tax enforcement was handled by private publishing companies owned mostly by to equites. Of course, the governor (in the rank of proconsul or proprietor) was not able to solve all problems alone, but his assistants were most often educated slaves. Public offices in Rome were not paid during the times of the republic – the governor had to support himself, so naturally, no lower-ranking officials were employed. He was assisted by lower officers who combined civilian and military functions, and above all, the entourage of educated slaves. They were secretaries, scribes, archivists, etc. In the capital itself, for a change, there were more officials, but the principle of operation was similar. From the aile upwards, there was no professional clerk class. Each year, elections were held for individual offices, and they could be held for only one year, without the possibility of re-election. Participation in such elections was quite costly, the actual holding of office was even more so, so only the richest citizens, for whom it was supposed to be a springboard for their further career, were in fact competing.
So it turns out that finding a working intelligentsia from outside the social elite is not that easy. This group includes teachers (mainly rhetoric and philosophy), artists, property managers, etc. The problem was that there was a demand for such services, but the owner of the ham could not afford such frills, so it was the wealthy people who used their services. These in turn were not in the habit of employing people “full-time”. They just had slaves for it. This is where the real phenomenon of Roman society comes into play. As early as the fourth century, Aristotle was to be dismayed by the emergence of slave schools in Greece. Their enormous influx to Rome took place after the Macedonian wars, especially after the conquest of Greece proper and the fall of Corinth in 146 BCE. One of the most famous was Polybius of Megalopolis, the author of “Acts”, who was captured after the Battle of Pydna (168 BCE). He was lucky enough to become a slave to Scipio, fascinated by Greek culture and language. Colloquially speaking, at the court of Scipio, Polybius lived like a doughnut in butter, but he was still a slave, although the master treated him with respect and like a friend. However, this does not change the fact that people like Scipio did not need any intelligence for wage labour, since they could easily buy an educated slave (or get them in the war). In time, training more capable slaves became normal practice. It was similar in the case of property managers, artists and even architects. Some of them received freedom over time, but in practice, the status of a liberator did not change much. In the light of the law, the liberator was obliged to be grateful, and thus in fact he was still completely dependent on the former owner, but now he had the status of his client. Of course, sometimes eminent sculptors or architects working on commission appeared in the capital, but it was not a large group, and in addition, the overwhelming majority were outsiders. So it turns out that the demand for “liberal professions” in Rome was so small during the republic that… the middle class were slaves and freedmen, whose ranks were sometimes joined by immigrants. However, they did not enjoy too much social prestige. So it would appear that the Romans themselves did not have their own middle class, and if anything, it accounted for a negligible percentage among Roman citizens.
The situation changed dramatically only during the principate period. From Octavian Augustus, the gradual formation of a civil administration begins, and the number of officials begins to gradually increase. The process is very slow, however, and it is actually only in Trajan’s time that it begins to gain momentum. Suffice it to mention that until his time officium a rationibus (today we would say “finance ministry”), it was in the hands of either imperial slaves or freedmen! In the time of Tiberius, the most influential person in the state was the equite Sejanus, which must have irritated the ambition and the pride of the Roman senators. This is also the source of the terrible reputation of praetorian prefects, or administrators of imperial estates. After all, the emperor trusted his slaves much more than senators fighting for positions, influence and money, and a large part of the sources we have to know the epoch is of senatorial provenance. However, this is already material for separate considerations…
Ultimately, it turns out that the Romans, despite the enormous cultural and economic potential they had at their disposal, did not develop their own “middle class” during the republic. This gap was successfully filled by slaves, freedmen and foreigners coming to Rome – mainly Greeks. It is paradoxical that this very despised social group contributed to the “Hellenization” of Rome. Thanks to it, Greek tradition and culture had a strong influence on the history of Rome, and through it, we have received a large part of its heritage.