The first five of the six successions within this dynasty were notable in that the reigning emperor did not have a male heir, and had toadopt the candidate of his choice to be his successor. Under Roman law, an adoption established a bond legally as strong as that of kinship.
It was common for patrician families to adopt, and Roman emperors had adopted heirs in the past: the EmperorAugustus had adoptedTiberius, and the EmperorClaudius had adoptedNero.Julius Caesar,dictator perpetuo and considered to be instrumental inthe transition from Republic to Empire, adopted Gaius Octavius, who later became Augustus, Rome's first emperor. Moreover, there were often still family connections: Trajan adopted his first cousin once removed and great-nephew by marriage Hadrian, Hadrian made his half-nephew by marriage Antoninus Pius heir, and the latter adopted both Hadrian's half-great-nephew by marriage Marcus Aurelius (Antonius' nephew by marriage) and the son ofHadrian's original planned successor, Lucius Verus. Marcus Aurelius's naming of his son Commodus as heir was considered to be an unfortunate choice and the beginning of the Empire's decline.[1]
With the murder of Commodus in 192, the Nerva–Antonine dynasty came to an end. It was followed by a brief period of turbulence known as theYear of the Five Emperors which ended with the establishment of the newSeveran dynasty.
Nerva was the first of the dynasty.[2] Though his reign was short, it saw a partial reconciliation between the army, the senate and the commoners. Nerva adopted as his son the popular military leaderTrajan. In turn,Hadrian succeeded Trajan; he had been the latter's heir presumptive, and averred that he had been adopted by him on Trajan's deathbed.
In 138, after a long reign dedicated to the cultural unification and consolidation of the empire, the EmperorHadrian named Antoninus Pius his son and heir, under the condition that he adopt both Marcus Aurelius and Lucius Verus. Hadrian died that same year, and Antoninus began a peaceful, benevolent reign. He adhered strictly toRoman traditions and institutions, and shared his power with theRoman Senate.
Marcus Aurelius and Lucius Verus succeeded Antoninus Pius in 161 upon that emperor's death, and co-ruled until Verus' death in 169. Marcus continued the Antonine legacy after Verus' death as an unpretentious and gifted administrator and leader. He died in 180 and was followed by his biological son, Commodus.
From the study of this history we may also learn how a good government is to be established; for while all the emperors who succeeded to the throne by birth, exceptTitus, were bad, all were good who succeeded by adoption; as in the case of the five from Nerva to Marcus. But so soon as the empire fell once more to the heirs by birth, its ruin recommenced.[5]
Machiavelli argued that these adopted emperors earned the respect of those around them through good governance:
Titus, Nerva, Trajan, Hadrian, Antoninus, and Marcus had no need of praetorian cohorts, or of countless legions to guard them, but were defended by their own good lives, the good-will of their subjects, and the attachment of the senate.[6]
Edward Gibbon wrote inThe History of the Decline and Fall of the Roman Empire that their rule was a time when "the Roman Empire was governed by absolute power, under the guidance of wisdom and virtue".[7] Gibbon believed that these benevolent monarchs and their moderate policies were unusual and contrasted with their more tyrannical and oppressive successors.