Marcus Aurelius
The Stoic philosopher-king who ruled at Rome's height, fought endless frontier wars, and left a timeless private journal.
Marcus Aurelius ruled the Roman Empire at its widest and wealthiest, and spent much of that reign in an army tent on the Danube, writing notes to himself about how to live and die well. Emperor from 161 to 180 CE, he was the last of the so-called Five Good Emperors, a run of rulers who each adopted a capable heir instead of handing power to a son. He is remembered less for anything he conquered than for a private notebook he never meant anyone to read.
The philosopher on the throne
Marcus owed his position to the emperor Hadrian's careful succession plan and came to the throne in 161 CE, at first sharing it with his adoptive brother Lucius Verus. Verus died in 169, and Marcus ruled alone thereafter. He had studied Stoicism seriously since boyhood, the Greek philosophy that prized self-command, acceptance of what lies beyond our control, and duty to the common good. Ruling at the height of the Pax Romana, the long internal peace of the empire, he tried to govern as a Stoic should, patiently and by the rules, even as the job kept getting harder.
War and plague
The peace was mostly on the inside. Marcus spent years on the northern frontier fighting the Marcomannic Wars against Germanic and Sarmatian tribes pushing across the Danube, and early in his reign faced a costly war with Parthia in the east. Worse than any enemy was the Antonine Plague, probably smallpox, which soldiers carried home from the eastern campaigns around 165 CE and which may have killed millions across the empire. Marcus governed through more than a decade of war and epidemic without ever, so far as we can tell, losing his composure.
Meditations, and one bad heir
On campaign he kept a journal in Greek, addressed to no one but himself, reminding himself to be just, to master his temper, and to accept death as part of nature. Centuries later it was published as the Meditations, and it remains one of the most quoted works of practical philosophy ever written. Yet the philosopher-king made one ruinous choice. He broke the chain of adoption that had given Rome a run of able emperors and left the throne to his own son, Commodus, whom he had raised to co-emperor in 177. When Marcus died in 180, worn down by nearly twenty years in the field, Commodus took sole power and proved vain, cruel, and unfit, and his reign is often marked as the point where Rome's long decline began. The Stoic who preached duty over blood could not, in the end, apply the lesson to his own family. His bronze likeness on horseback survived the Middle Ages only because Christians mistook it for the Christian emperor Constantine, and it still stands, much copied, on Rome's Capitoline Hill, while his Meditations have outlasted the empire he ruled.