The first five of the six successions within this dynasty were notable in that the reigning Emperor adopted the candidate of his choice to be his successor. Under Roman law, an adoption established a bond legally as strong as that of kinship. Because of this, all but the first and last of the Nerva-Antonine emperors are called Adoptive Emperors.
The importance of official adoption in Roman society has often been considered as a conscious repudiation of the principle of dynastic inheritance and has been deemed as one of the factors of the period's prosperity. However, this was not a new practice. It was common for patrician families to adopt, and Roman emperors had adopted heirs in the past: The Emperor Augustus had adopted Tiberius and the Emperor Claudius had adopted Nero. Julius Caesar, dictator perpetuo and considered to be instrumental in the transition from Republic to Empire, adopted Gaius Octavius, who would become Augustus,
With Commodus' murder in 192, the Nerva-Antonine dynasty came to an end; it was followed by a period of turbulence known as the Year of the Five Emperors.
The rulers commonly known as the "Five Good Emperors" were Nerva, Trajan, Hadrian, Antoninus Pius and Marcus Aurelius. The term was coined by the political philosopher Niccolò Machiavelli in 1503:
Machiavelli argued that these adopted emperors, through good rule, earned the respect of those around them:
The 18th-century historian Edward Gibbon, in his work The History of the Decline and Fall of the Roman Empire, opined that their rule was a time when "the
Gibbon went so far as to state: