They were Nerva, Trajan, Hadrian, Antoninus Pius, and Marcus Aurelius, who reigned from 98 to 180 AD – a period that marked the zenith of the Roman Empire in terms of territorial extent, economic prosperity, arts and architecture.
The first to call them the "good emperors" was Niccolò Machiavelli in his “Discourses on the First Decade of Titus Livius”, written in the early 16th century: «All the emperors who succeeded to the empire by hereditary right – with the exception of Titus – were bad; those who succeeded by adoption were all good, as were the five from Nerva to Marcus Aurelius…».
In the late 18th century, Edward Gibbon, in his “History of the Decline and Fall of the Roman Empire“, went even further, writing: «If a man were called to fix the period in the history of the world during which t
he condition of the human race was most happy and prosperous, he would, without hesitation, name that which elapsed
from the death of Domitian to the accession of Commodus».However, as with all historical events, one must critically examine both modern historiographical interpretations and ancient sources – the latter of which were certainly not impartial.
The eighty years of the "five good emperors" were a period of stability and economic prosperity, but
there were also negative aspects.
First of all, those five emperors were tough and determined men of power who had sought and maintained their authority by any means necessary, overcoming hostility, betrayal, and conspiracies.
Although
the emperor’s power was absolute, it depended on his ability to win the favor of the Senate and the aristocracy, of the army and the equestrian class, and – last but not least – the common people. Otherwise, he risked meeting the same destiny as Julius Caesar, Nero, or Caracalla.
During the imperial era – beginning as early as the time of Augustus – the main
problem was ensuring a stable and lasting succession to power, in order to avoid new dictatorships or civil wars. The true core of the question was always
the power struggle between the Senate and the army: both the aristocracy and the military sought to choose the emperor themselves, ensuring he would serve their respective – and inherently conflicting – interests.
Augustus himself had to bow to the authority of the Senate, calling himself “primus inter pares“ (first among equals) to mask what would, in practice, become a hereditary monarchy. Since he had no male heirs, he opted for adoption, choosing Tiberius and compelling him, in turn, to adopt his own nephew, Germanicus. Through the system of adoption, power remained within the Julio-Claudian dynasty until the reign of Nero.
In 69 AD, following the death of Nero and the ensuing conflict between Galba, Otho, and Vitellius – each one supported by his own army –
Vespasian ascended to the throne. He restored hereditary succession by designating his two sons, Titus and Domitian, as his successors. The latter –
Domitian – consolidated power in his own hands, progressively diminishing the authority of the Senate; consequently, Tacitus and Suetonius (both senators), as well as Pliny the Younger (who authored the “Panegyric of Trajan” to celebrate that emperor’s virtues), described Domitian as a bloodthirsty tyrant and a depraved monster.
In recent times, both
Domitian and Nero have been in some aspects "rehabilitated" by modern historians, who moved past the age-old prejudice of their “damnatio memoriae“ (condemnation of memory).
But let us now turn to the "five good emperors."The first was Nerva (Marcus Cocceius Nerva), who reigned for only two years, from 96 to 98 AD. His brother had married a great-granddaughter of Tiberius, making him a relative of the Julio-Claudian dynasty – a fact that formally legitimized his nomination. Nerva restored harmony to the empire by re-establishing good relations with the Senate. With him the Antonine dynasty began; having no children of his own, he once again used adoption, choosing Trajan – an excellent general who was highly regarded by the army.
The second was Trajan (Marcus Ulpius Nerva Traianus), the warrior-emperor, who reigned from 98 to 117 AD. He brought the Roman Empire to its greatest territorial extent, conquering Dacia to seize its immense wealth, which in turn funded major public works. Having no children, on his deathbed he adopted Hadrian, to whom he was related through his marriage to Vibia Sabina, Trajan’s great-niece.
The third was Hadrian (Publius Aelius Traianus Hadrianus), who reigned from 117 to 138 AD. To consolidate and defend the borders against barbarian incursions, he chose to abandon some territories. He traveled throughout the empire to see firsthand how it was being administered and managed. A lover of the arts and architecture, he left some of the most magnificent monuments of Roman antiquity. Having no children, he adopted Antoninus Pius, stating that he, in turn, must adopt his nephews, Marcus Aurelius and Lucius Verus.
The fourth was Antoninus Pius (Titus Aurelius Fulvus Boionus Arrius Antoninus), who reigned from 138 to 161 AD and always stayed in Rome. During this period, the empire enjoyed significant economic stability, with peace and steady conditions, along with important administrative reforms that completed those of Hadrian.
The fifth and final one was Marcus Aurelius (Marcus Aurelius Antoninus Augustus) who reigned frpm 161 to 180 AD. He was the philosopher-emperor and ruled with wisdom and justice, yet had to faces with epidemics (plague) and wars to defend increasingly insecure borders.
With the accession of his son
Commodus, who reigned from 180 to 193 AD, the Antonine dynasty came to an end. A period of economic crisis ensued, brought on by wars, barbarian invasions, plague, and problems related to the succession to power. These were endemic problems for the empire, which –
at the end of the Severan dynasty in 235 AD – would culminate in the
Crisis of the Third Century, also known as the period o
f Military Anarchy.