'Principate' is etymologically derived from the Latin word princeps, meaning chief or first, and therefore represents the political regime dominated by such a political leader, whether or not he is formally head of state or head of government. This reflects the principate emperors' assertion that they were merely "first among equals" among the citizens of Rome.

Under the Republic, the princeps senatus, traditionally the oldest or most honored member of the Senate, had the right to be heard first on any debate.^[6] Scipio Aemilianus and his circle had fostered the (quasi-Platonic) idea that authority should be invested in the worthiest citizen (princeps), who would beneficently guide his peers, an ideal of the patriot statesman later taken up by Cicero.^[7]

In a more limited and precise chronological sense, the term Principate is applied either to the entire Empire (in the sense of the post-Republican Roman state), or specifically to the earlier of the two phases of Imperial government in the ancient Roman Empire before Rome's military collapse in the West (fall of Rome) in 476 left the Byzantine Empire as sole heir. This early Principate phase began when Augustus claimed auctoritas for himself as princeps, and continued (depending on the source) up to the rule of Commodus, of Maximinus Thrax, or of Diocletian.^[8]

The title, in full, of princeps senatus / princeps civitatis ("first amongst the senators" / "first amongst the citizens") was first adopted by Octavian Caesar Augustus (27 BC–AD 14), the first Roman "emperor," who chose not to reintroduce a legal monarchy. Augustus likely intended to establish political stability desperately needed after the exhausting civil wars by a de facto dictatorial regime within the constitutional framework of the Roman Republic – what Gibbon called "an absolute monarchy disguised by the forms of a commonwealth"^[9] – as a more acceptable alternative to, for example, the early Roman Kingdom.

Although dynastic pretenses crept in from the start, formalizing this in a monarchic style remained politically perilous;^[10] and Octavian was undoubtedly correct to work through established Republican forms to consolidate his power.^[11] He began with the powers of a Roman consul, combined with those of a Tribune of the plebs; later added the role of the censor and finally became pontifex maximus as well.^[12][13]

In addition to these legal powers, the principate was also characterized by the emperor being the "ultimate source of patronage".^[14] This was due in part to their immense wealth, being named Pater Patriae or "father of the country"^[15], and by having a monopoly on political power. To this, emperors would satisfy the senatorial class with appointments to the high offices and to the provinces, effectively removing threats to their power in Rome. As such, emperors went to great lengths to control and satisfy the needs of the army (their ultimate source of power) by proving gracious donatives to the troops upon their ascension and for special events; limiting senatorial control over the legions by way of controlling military provinces through "extraordinary military commands"; and using oaths to bind the military to the emperor personally.^[16][17]

Tiberius, like Augustus, also acquired his powers piecemeal, and was proud to emphasize his place as first citizen: "a good and healthful princeps, whom you have invested with such great discretionary power, ought to be the servant of the Senate, and often of the whole citizen body".^[18] Thereafter, however, the role of princeps became more institutionalized: as Dio Cassius puts it, Caligula "took in one day all the honours which Augustus had with difficulty been induced to accept".^[19]

Nevertheless, under this "Principate stricto sensu", the political reality of autocratic rule by the emperor was still scrupulously masked by forms and conventions of oligarchic self-rule inherited from the political period of the 'uncrowned' Roman Republic (509 BC–27 BC) under the motto Senatus Populusque Romanus ("The Senate and people of Rome") or SPQR. Initially, the theory implied the 'first citizen' had to earn his extraordinary position (de facto evolving to nearly absolute monarchy) by merit in the style that Augustus himself had gained the position of auctoritas.

Imperial propaganda developed a paternalistic ideology, presenting the princeps as the very incarnation of all virtues attributed to the ideal ruler (much like a Greek tyrannos earlier), such as clemency and justice, and military leadership,^[21] obliging the princeps to play this designated role within Roman society, as his political insurance as well as a moral duty. What specifically was expected of the princeps seems to have varied according to the times, and the observers:^[22] Tiberius, who amassed a huge surplus for the city of Rome, was criticized as a miser,^[23] while his successor Caligula was criticized for his lavish spending on games and spectacles.^[24]

Generally speaking, it was expected of the Emperor to be generous but not frivolous, not just as a good ruler but also with his personal fortune (as in the proverbial "bread and circuses" – panem et circenses) providing occasional public games, gladiators, chariot races and artistic shows. Large distributions of food for the public and charitable institutions also served as popularity boosters, while the construction of public works provided paid employment for the poor.

After his victory at Actium in 31 B.C., Octavian, the adoptive son and heir of Caesar, became the sole ruler of Rome and its Empire.^[25] With support from the army and allies from various backgrounds, he concentrated immense power in his hands, built upon the accumulation of former republican magistracies. From 31 to 27 B.C., he established a new regime: the Principate.^[26] In a Senate session on January 27 B.C., he appeared to restore the res publica (the Republic) by returning it to the Senate and the people. However, in practice, the Senate retained control over only a few provinces without legions. Octavian, who soon after received the title of Augustus, kept his vast powers and was entrusted with the administration of frontier provinces, thereby holding command over the armies.^[27] Augustus's title highlighted his sacred and divine character, giving his decisions considerable weight even though they lacked an official institutional basis.

In 23 B.C., he was granted full and lifelong tribunician power, the civilian foundation of his authority, and a majus proconsular imperium (greater than that of the proconsuls of the senatorial provinces). In 2 B.C., he was awarded the title Father of the Country,^[28] symbolically placing the entire Roman people under his protection. Everywhere, he was seen as the "first citizen", the princeps. Augustus influenced the election of magistrates through recommendations, and directed foreign policy and diplomacy. He commanded significant financial resources through his personal wealth (partially inherited from Caesar), revenues from Egypt (his private domain), and various taxes.^[27] However, as he spent heavily on administration, wars, and the upkeep of 200,000 impoverished citizens, the Empire’s budget faced difficulties towards the end of his reign. Augustus lost all his direct heirs in succession, so he prepared his stepson, Tiberius, to succeed him without challenge.^[29]

Augustus relied on homines novi or “new men”: knights, military men, prominent figures from Italian towns, and senators who had joined his cause in hopes of securing key positions.^[30] Conservative by nature, he pursued policies that restricted slaves and limited manumissions. Favoring moral order and family values, he enacted laws against celibacy and "immoral behavior."

Augustus completed the pacification of the Cantabri and Astures in Spain. The Empire expanded to the Danube with the creation of the provinces of Moesia and Pannonia. The Alpine peoples were finally subdued by Tiberius and Drusus, and divided into the provinces of Noricum, Raetia, and the Maritime Alps.^[31] The prolonged war against the Germans led the army as far as the Weser and Elbe rivers. However, in the year 9, the Germanic leader Arminius revolted, annihilating three legions under Varus in the Teutoburg Forest. Germania was ultimately abandoned by Tiberius in 17, and two sectors along the left bank of the Rhine were then called Germania.^[25][27]

Tiberius (14-37), the son of Livia from her first marriage and stepson of Augustus, became emperor at the age of 56, having already proven himself as a remarkable military leader. Highly conservative, he ruled in line with Augustus' policies.^[32] Augustus had compelled him to adopt Germanicus, who was intended as his successor. However, Germanicus died in the East in 19. Sejanus, the prefect of the Praetorian Guard, then maneuvered to make himself indispensable to Tiberius, eliminating rivals from the imperial family. Eventually, he was denounced by Antonia, Germanicus' mother, arrested, and swiftly executed. Tiberius ended his reign by instilling terror in Rome and condemning many senators.^[32] Unlike Augustus, however, Tiberius was a frugal emperor.^[27]

Caligula (37-41), the son of Germanicus, was soon accused of madness and was assassinated by his own guard before completing his fourth year of rule. The Praetorians then hailed Caligula’s uncle, Claudius I (41-54), one of the few survivors of Sejanus’ schemes, as emperor.^[33]

Under Claudius, the freedmen Narcissus and Pallas established the imperial chancery and the fiscus (imperial treasury), providing the emperors with the institutions they had previously lacked.^[34] Claudius was supportive of the promotion of provincials, granting citizenship to several Alpine peoples and even admitting notable Gauls from Transalpine Gaul (beyond Cisalpine Gaul and Provence) into the Senate. He completed the conquest of Mauretania and began imposing Roman rule in Britain.^[27]

The imperial court was a hotbed of intrigue. Claudius' fourth wife, Messalina, was unfaithful to him, eventually leading to her execution.^[35] Agrippina, his niece and fifth wife, schemed to the extent that she succeeded in getting the emperor to adopt her son from a previous marriage, Nero. In 54, she poisoned the emperor, and despite his age of only 17, the Praetorians accepted her son as emperor.^[35]

Nero initially ruled under his mother’s influence but had her assassinated in 59. He followed the guidance of Burrus and the younger Seneca until Burrus' (natural) death in 62.^[36] Afterward, he dismissed Seneca and ruled alone.^[37]

After Nero’s suicide in 68 AD, the Roman Empire faced a political crisis known as the Year of the Four Emperors.^[38] This period of turmoil saw the successive rise and fall of Galba, Otho, and Vitellius, each declared emperor by their respective legions but swiftly overthrown.^[39] Stability was restored when Vespasian (69–79), a general commanding the Eastern armies, emerged victorious. Supported by his military might and the allegiance of the Praetorian Guard, Vespasian founded the Flavian dynasty, ushering in an era of consolidation and reform.^[38]

Vespasian is credited with stabilizing the Empire’s finances, heavily depleted after Nero’s reign and the civil wars, by imposing new taxes and restoring discipline in provincial governance.^[38] His reign also saw the beginning of major construction projects, including the initiation of the Flavian Amphitheatre, better known as the Colosseum, which symbolized Roman engineering prowess and cultural grandeur.^[32]

His elder son, Titus (79–81), succeeded him and is remembered for his military success during the Jewish War, culminating in the capture of Jerusalem in 70 AD and the destruction of the Second Temple. Despite his brief reign, Titus won the favor of the Roman populace for his generosity in responding to disasters such as the eruption of Mount Vesuvius in 79 AD and a fire in Rome.^[39]

Domitian (81–96), the younger son, consolidated the gains of his predecessors but ruled with an increasingly autocratic style.^[39] He expanded the Empire's frontiers, strengthening defenses in Germania and Britain, and enhanced the administrative efficiency of the imperial government, particularly in the provinces.^[35] However, his authoritarian rule and the execution of many senators led to growing discontent among Rome’s elite. Ultimately, he was assassinated in 96 AD in a palace conspiracy, bringing the Flavian dynasty to an end.^[38][35]

Despite the dynasty's controversial reputation, the Flavians left a lasting legacy by restoring stability to the Empire, promoting monumental architecture, and laying the groundwork for the prosperity of the subsequent Antonine period.^[35]

The Senate had already chosen a replacement in the person of Nerva (96-98), who founded the Antonine dynasty.^[40] He adopted his successor, Trajan (98-117), a Roman from Hispania. Five out of six remarkable emperors in this dynasty selected their successor during their lifetimes, as they had no sons, yet the choice always fell on close relatives.^[40] The reigns of Trajan and his successor Hadrian (117-138) mark the peak of the Roman Empire.^[41] Trajan, while fostering agriculture and developing the administration, conquered Dacia, the Parthian Empire, and annexed Arabia. However, the conquest of Parthia did not last beyond him.^[41]

Emperor Hadrian focused on a more defensive policy. During his reign, significant fortifications developed in various border regions, notably in Africa and Britain, often referred to as limes.^[41] Additionally, Hadrian worked to improve the empire's functioning. Continuing efforts begun by previous emperors, he promoted the integration of provincials, notably through the creation of honorary colonies: while the term colony once mainly referred to the settlement of Roman colonists, it now became an honorary title for a city, granting Roman citizenship to all its inhabitants.^[41][42]

Under Antoninus Pius (138-161), a new distinction appeared in law between the honestiores (wealthy) and humiliores (poor), with the latter facing harsher punishments for the same offenses.^[43] Marcus Aurelius (161-180), known as a Stoic philosopher-emperor, spent 15 years on the Danube frontier fighting against barbarian invasions. The empire was entering a less favorable period: its neighbors at the borders seemed more powerful, it faced agrarian difficulties, famines, and the outbreak of the Antonine Plague.^[44] Marcus Aurelius chose his son, Commodus (180-192), as his successor. Commodus' assassination ended the Antonine dynasty.^[35]

The assassination of Commodus, the last of the Antonines, in December 192, opened a political crisis similar to the one at the end of the Julio-Claudian dynasty. The Praetorian Guard assassinated the new emperor Pertinax and brought Didius Julianus to power through an auction for the imperial title.^[35][45] Ultimately, the general of the Danube army, the African Septimius Severus (193-211), took power in 193. He rewarded the army by increasing its ranks and strengthening imperial power.^[46] The Praetorians, who had made and unmade many emperors, were recruited from the Danube legions^[38] loyal to Septimius Severus. The cultural mixing brought by the empire increased, and religions from the East became more popular in the Empire, particularly the cult of Mithras among the military.^[47][48] This aspect has sometimes been exaggerated by historians, who described the Severans as an Eastern dynasty, a judgment that is now considerably revised.^[29]

Severus named his two sons Augustus, but upon his death, Caracalla (211-217) hastily killed his young brother Geta.^[49] Caracalla is remembered for the Edict of 212 (Constitutio Antoniniana), which granted Roman citizenship to nearly all free inhabitants of the Empire, significantly altering its social structure.^[50][51] However, Caracalla was assassinated on the Parthian front by the Praetorian Prefect Macrinus (217-218), who briefly succeeded him but failed to hold onto power for long.^[26]

Caracalla’s cousin, Elagabalus (218-222), then became emperor, primarily under the influence of his grandmother, Julia Maesa, who had orchestrated his ascent. Elagabalus’ fixation on the cult of the sun god Elagabal led to widespread dissatisfaction and unrest, culminating in his assassination by the Praetorians.^[52] His cousin Severus Alexander (222-235) succeeded him, but his relatively weak leadership and reliance on his mother’s advice alienated the military.^[53] After Severus Alexander’s assassination, the Empire entered a period of severe instability, often referred to as the "Crisis of the Third Century" or "military anarchy." Although imperial power fluctuated, it was never entirely absent during this tumultuous era.^[54][55]

The emperors hold the title of imperator, the supreme commander of the armies. Throughout the Roman Empire, victory was a powerful factor in strengthening imperial power. A defeated emperor could easily have his power contested by ambitious generals.^[35][46] All emperors made it a habit to be elected consul to demonstrate the continuity between republican institutions and the principate. This also grants them imperium, or the authority to command. They also held imperium proconsulare, which gave them the power to govern all provinces. As holders of potestas tribunicia, they possessed intercessio, the right to oppose any decision made by the magistrates of the empire. Like Julius Caesar, they carried the title of pontifex maximus, making them the heads of Roman religion.^[45][56] They also received an oath of personal loyalty from all inhabitants of the Empire. Thanks to imperium, the emperor was all-powerful.^[29][26]

Both the Senate and the people were deeply fearful of civil war with each succession. Therefore, they eagerly accepted the idea that a descendant of the reigning prince would succeed his father. One of the emperor’s duties was to ensure a peaceful transmission of the throne. The most logical choice, even in the eyes of the Romans, was to designate his son or adopt one. When a reigning emperor successfully passed on his power to a successor, it was seen as the completion of a successful reign.^[57][58] In fact, while hereditary succession was not a principle of public law, it was an aristocratic practice accepted by Roman opinion. In times of crisis, a general celebrated in triumph by his soldiers could, through military force, rise to the supreme power.^[38][53] The Praetorian Guard, tasked with guarding the emperor’s security, played an increasing role in the plots and assassinations that marked the imperial period.^[54]

The role of pontifex maximus bestowed upon emperors a sacred character. Additionally, in popular belief,^[56] figures like Scipio Africanus, Marius, and Sulla had a divine character. Caesar developed a legend of divinity around himself, claiming descent from Venus and Aeneas.^[35] Emperor Augustus established the imperial cult, deifying Caesar, and as his heir, he elevated himself above humanity.^[58][29] He proclaimed himself the son of Apollo. Augustus also associated the entire community with the cult of the family genius, thus becoming the father of all, which is why he earned the title pater patriae (father of the fatherland).^[45] Augustus refused to be deified during his lifetime but allowed temples and altars dedicated to him, especially in the East, where it was common for rulers to be viewed as living gods, provided his name was associated with the deified Rome. This movement continued after his death. All emperors aligned themselves with the protection of a god.^[26] Gradually, they were seen as living gods throughout the Empire.^[53] After their deaths, they received apotheosis. The Antonines, for example, placed Jupiter Capitolinus as the supreme god, but when in Greece, Hadrian invoked Zeus Olympios or Panhellenios, accompanied by Tyche (Fortune) as protector.^[59] During his reign, the divinization of the living emperor further progressed, especially in the East. The imperial ideology took on more philosophical aspects, where the emperor’s success was attributed to his merit (virtus) and divine protection.^[60]

The imperial cult also served as a means of uniting the diverse peoples of the Empire, with their varying cultures and beliefs, around respect for Roman power through the deified emperor.^[54] Across the Empire, temples dedicated to the imperial cult were either restored or newly constructed. Ceremonies were held in honor of the emperor, providing an opportunity for the community to gather in processions, engage in sacrifices, enjoy banquets, and participate in various spectacles.^[61]

Between the reign of Augustus and that of Commodus, the Roman Empire underwent profound changes, especially in the West. The provinces became significantly Romanized: many provincials were granted Roman citizenship, and Roman ways of life and symbols spread. The use of Latin, Roman urban planning, and public baths became cultural traits shared primarily by the local aristocracies at first, from Africa to Caledonia.^[56][58][62] This gradual integration of provincials changed the composition of the ruling class of the empire. By the 160s, only half of the senators were still from Italy, with the rest coming from the East, Gaul, Hispania, Africa, and other regions.^[29][53] However, these great senatorial families, as well as the upper echelons of the equestrian order, were thoroughly Romanized, regardless of their origins, with multiple marriages and alliances diminishing the significance of these regional backgrounds.^[41]

For the empire's leaders, it became a shared heritage administered in the name of the emperor. While attachment to one's homeland was still respected as a sign of the vitality of civic ideals, it was Roman identity, or Romanitas, that provided the foundation for a common political space.^[54] For the more modest populations, the changes were also profound, though more difficult to discern: Latin spread even among the humbler people, even if local languages persisted, and Roman ways of life were widely adopted.^[45] With the stabilization of the borders, the Roman army organized itself around large camps and border regions, and the recruitment of soldiers became increasingly regional, without compromising the army's quality.^[63][55]

The Roman Empire was divided into provinces, each with distinct administrative structures.

In the senatorial provinces, the governor, either a proconsul or a propraetor, was appointed by the Senate. During Augustus’ reign, these governors were selected by lot for a one-year term and assisted by quaestors who handled financial administration. A procurator, a member of the equestrian order, managed the emperor's interests, such as mines, estates, and special taxes. The senatorial provinces were peaceful, and no legions were stationed permanently in them.^[29][58]

In the imperial provinces, the governor, a legate or procurator, was appointed by the emperor. Egypt, in particular, was governed by a prefect from the equestrian order appointed by the emperor. However, the emperor had oversight powers over all provinces, even appointing extraordinary legates in the senatorial provinces.^[62][45] Italy, unlike other provinces, had a privileged status. All free inhabitants of Italy were Roman citizens and were exempt from land taxes.^[63][41]

Italy was not considered a province but was directly administered by the Senate of Rome. Under the reign of Hadrian, it was divided into four districts that were not under the Senate's control. This division was reversed by Hadrian's successor, Antoninus Pius, following pressure from the senators.^[45][53]

Governors were typically appointed for terms not exceeding three years. They maintained close communication with the central government through ongoing correspondence. Their duties included overseeing taxes, maintaining public order, conducting censuses, and ensuring the protection of property.^[56] Governors had minimal administrative staff, and their primary involvement in provincial life was in judicial matters, managing disturbances, and addressing financial difficulties within cities. Most administrative tasks were handled locally within the city framework, which was considered by Romans to be the ideal way of life. Where cities did not exist, especially in the West, the Romans established them. The more just administration of the Empire compared to the Republic helped the inhabitants of the provinces to form a deeper attachment to Roman rule.^[54][55]

In the capital, the emperor was assisted by various bodies and individuals in governance. The imperial council, which helped in making key decisions, consisted of men chosen for their military, legal, or diplomatic expertise. Over time, the council became permanent and gained significant influence in the governance of the Empire. Hadrian restructured the council, predominantly selecting jurists.^[64] The praetorian prefect was one of the most important figures in the imperial entourage, commanding the Praetorian Guard and serving as second-in-command during military expeditions. His growing power even posed a threat to the imperial authority. Under Augustus, the highest positions were held by members of the senatorial or equestrian classes, while lower positions were given to the emperor's freedmen or even slaves from his household.^[65] This system remained in place until the reign of Hadrian, who entrusted the management of offices to equestrians, relegating the freedmen to subordinate roles.^[66][67]

Until the mid-2nd century, the Roman army remained a force of conquest. Augustus annexed Illyricum and unsuccessfully attempted to conquer Germania. He established the Rhine and Danube as the Empire's borders. Claudius conquered Britain, and Trajan expanded into Dacia, Arabia, and briefly Parthia.^[42] From Hadrian onwards, the primary focus shifted from territorial expansion to maintaining the Empire. Hadrian abandoned Armenia, Mesopotamia, and Assyria, establishing peace with the Parthians. The eastern border of the Empire became the Euphrates, consolidated by the limes.^[55][45]

One of Hadrian’s priorities was to protect the Roman Empire from barbarian invasions, leading him to build the famous Hadrian's Wall in northern Britain. This wall stretched 120 km from the mouth of the Tyne River to Solway,^[41] featuring 300 towers and 17 fortified camps.^[42] In Germania, the Decumates Fields were similarly protected by limes running from Mainz to Regensburg.^[64][63][54] Hadrian’s successors continued this fortification strategy along the borders of Germania, the East, and Africa, erecting walls and structures that eventually earned the collective name "limes" (in Latin, meaning a border patrol road). Strategic roads were built to facilitate movement and defend against attacks, covering a total of 9,000 km of frontier.^[53]

The Roman army, focused on defending these borders, was composed of around 400,000 soldiers spread across 30 legions. The soldiers included about 150,000 Roman citizens who served for 20 years, supplemented by auxiliary troops recruited from non-citizens. These auxiliaries were granted Roman citizenship after 25 years of service. From Hadrian’s time, some auxiliary troops maintained their traditional arms and practices,^[62] distinguishing them from the Roman legions.^[68] The Romans faced increasing difficulty recruiting soldiers from Italy, as the Italian population increasingly resisted military service. Consequently, recruits were drawn from provinces, particularly those less Romanized. While the Praetorian Guard and officers (centurions) continued to be recruited from Italy, the army as a whole became a professional force composed of various peoples from across the Empire.^[56]

The cohesion of the Roman army was founded on rigorous training, strict discipline, and a distinctive religious culture centered around traditional Roman gods and the imperial cult. The military engineers were responsible for constructing vital infrastructure like canals, roads, aqueducts, and fortifications of cities.^[66][67] The army’s presence along the borders played a significant role in the economic development of these regions and was a powerful tool of Romanization.^[29][58]

The 80 million inhabitants of the Roman Empire belonged to different social groups based on birth or wealth. One could be born a slave, a free man, or a Roman citizen. Slaves had no rights and led very harsh lives, often working in large estates or mines. In the cities, their condition was somewhat better as they worked as domestics, craftsmen, and even teachers or artists for the more educated ones.^[69][70] Some slaves ran shops and paid their masters for the privilege of working, which allowed them to save for their manumission (freedom).^[71]

The subjects of the Empire were free men who were not Roman citizens. They could testify in court but were required to pay the tributum, a direct tax.^[72] Roman citizenship could be obtained by birth, decree, or after 25 years of military service.^[73] Roman citizens did not pay the tributum. Most citizens had modest occupations, and in Rome, 200,000 poor citizens relied on free grain distributions (the annona) to survive.^[74][62]

The wealthiest individuals were part of the equestrian or senatorial orders, appointed by the emperor. In this hierarchical society, there were distinctions between the senatorial order and the decurional order. During Augustus's reign, the equestrian order was at his disposal and became the main source of imperial administration.^[53] Nobilitas (nobiles) were defined by one's origin rather than status, though over time, the social markers of nobilitas diminished. By the 2nd century, the procession of portraits, once an important symbol of status, had become reserved solely for imperial funerals.^[75][41]

In the early Empire, society was not rigidly fixed. Slaves, especially those in urban areas, could often be freed by their masters.^[27] Gradually, all free men gained citizenship, and in 212 AD, the Edict of Caracalla made all free men Roman citizens, although dediticii (Barbarians) were excluded from this privilege.^[29][45] For instance, in Volubilis, the isolated peasants and semi-nomadic tribes around the city remained subjects of the Empire, with a few leaders rewarded with citizenship for their loyalty.^[76][63]

Over time, distinctions were made between the honestiores (the powerful) and the humiliores (the humble). These social categories replaced the earlier legal distinction between citizens and non-citizens, with the rich and powerful receiving preferential treatment in the courts over the poor.^[66][56]

In almost all cities of the empire, life revolved around Roman times. According to some estimates, Rome, the capital, had over one million inhabitants during the High Empire.^[77] The Romans simply referred to it as urbs, the city. It was, along with Alexandria, the largest city in the Roman world. Since the 1st century, the city had been greatly beautified by the emperors, with numerous monuments symbolizing the grandeur of Rome and the Roman way of life. The forums, which were places for political life during the Republic, transformed into monumental complexes including basilicas, many temples, triumphal arches, and libraries.^[77] The Palatine Hill was home to the imperial palaces, including the House of Augustus. However, Rome was primarily, in the popular imagination, known as the city of games. Several exceptional monuments were dedicated to these, such as the Circus Maximus between the Palatine and Aventine hills, and the Colosseum, the largest amphitheater in the Roman world, dedicated to ludi (public games), particularly gladiatorial combat.^[78]

The Roman baths appeared at the end of the Republic, and emperors built many baths for the entertainment of the Roman plebs.^[79] To provide the water needed for the baths and the growing population, many aqueducts were constructed. By the 1st century, these aqueducts could deliver up to 992,000 cubic meters of water to the city every 24 hours.^[80] Rome had grown in a disorganized manner over the centuries. The streets were narrow and winding. After the great fire of Rome in 64 AD, Nero had the city rebuilt with wider, more spacious roads. The wealthiest lived in large villas, while the poorer classes resided in apartment buildings, known as insulae.^[81]

Major cities such as Carthage and Antioch flourished. The Romans built cities across the Empire following the regular grid plan called the hippodamian plan. The city was organized around two main streets: the cardo (north-south axis) and the decumanus (east-west axis). Typical Roman monuments were found in these cities, including forums, basilicas, temples, and amphitheaters. Each city was headed by a local senate called the curia, composed of wealthy citizens of the Empire, forming the ordo decurionum.^[80] It was within this council that magistrates were elected: aediles (in charge of market and street police), duumviri (magistrates with judicial responsibilities), and duumviri quinquennales (elected every five years to take on censorial functions). The ordo decurionum was responsible for managing the city's finances (pecunia publica), maintaining public order, and dealing with the central power.^[81]

The decurions and, particularly, the magistrates, financed much of the construction of monuments and temples from their own funds. They could also voluntarily add a personal donation to legally required sums. This practice, known as evergetism, played a significant role in the construction and life of the cities. Evergetism allowed the city's aristocrats to demonstrate their generosity and wealth, often serving as a tool for self-celebration, supporting family strategies, and ensuring political cohesion.^[77] The monument donated would remind future generations of the family's glory, while at the same time, strengthening political and social unity. Evergetism could also be seen as a reciprocal act, a counter-gift that responded to the respect the city showed the donor and the political power it granted. Festivals, spectacles, and various distributions, often stemming from evergetism, contributed to the creation and maintenance of a municipal culture and civic unity in the cities.^[78] While past historiography suggested that evergetism might explain the abandonment of political duties by local aristocracies, this hypothesis is no longer widely accepted, and it is now understood that there was no widespread desertion of the curiae.^[77]

In the western cities of the empire, Latin spread, while the east remained faithful to the Greek language.^[82]

In general, most of the wealth produced comes from the countryside and agriculture. Under the High Empire, the trend toward land concentration continued. The nobilitas (Roman aristocracy) and Eastern temples owned vast estates. However, the largest landowner in the empire was the emperor himself, who expanded his properties by confiscating those of his opponents.^[83] The center of the large estate, or latifundium, was the Roman villa, the master's residence with its dependencies. While the ideal was autarky, as landownership and self-sufficiency were considered the foundation of social dignity, there were also significant regions dedicated to commercial crops. The main crop was grain, which fed the entire population of the estate.^[72] Roman agronomists advised reserving part of the land for commercial crops like vines and olive trees. Small property did not disappear; it remained the ideal in Roman society, but its importance decreased. Although agriculture remained technically stagnant under the Empire, certain practices spread, and some authors suggest that productivity gains may have occurred.^[67]

The main artisanal activities took place in both rural areas and cities: textile production, tool manufacturing and maintenance, and pottery production. For a long time, historians considered ancient cities as merely consumer hubs, but after significant debate, this view has been significantly revised.^[67] Important mining regions existed in Spain and the Danubian regions, though here too, technological progress was minimal. Manual labor and mercantile activity were considered beneath the educated classes, and reserved for lower classes and slaves. The existence of slaves may have also hindered technological progress. However, recent archaeological research has strongly revised these judgments, with archaeologists and historians agreeing on the significant and early diffusion of watermills in the Roman Empire.^[72]

The peace and prosperity of the High Empire led to an increase in commercial activities. The Mediterranean at the heart of the Roman Empire witnessed intense trade. Piracy was greatly reduced thanks to the emperor's naval fleets which were in patrol constantly.^[83] Ships increasingly ventured into the open sea to shorten travel times, but for shorter or medium-range trips, sailors preferred coastal cabotage. Navigation in the Mediterranean was allowed from March to October, and no navigation occurred during the winter months. Major Mediterranean ports included Ostia (Rome’s port), Alexandria in Egypt, and Carthage in Africa.^[74] Commercial links also extended to the Baltic, and sub-Saharan Africa via trans-Saharan caravans, India, and China, showing that the empire was not a closed space.^[84] Romans’ taste for luxury goods fueled international trade. In this sense, the Empire extended the last two centuries of the Republic, but over time, Italian economic dominance in areas such as high-quality ceramics, amphorae, and wines gradually gave way to provincial productions.

• Constitution of the late Roman Empire
• Constitutional reforms of Augustus
• How Rome Fell by Adrian Goldsworthy
• Roman emperor