When I think about Marcus Aurelius, I remember not only his stoic philosophy, which I often think of, but that he made one of the worst blunders any emperor ever made. The previous four emperors had chosen as their successor, a qualified adult, who they adopted as a son. Marcus chose his son Commodus, who was unfit for the position. After a chaotic reign of 12 years, Commodus was assassinated, and Rome was not well governed again until the reign of Diocletian a century after Marcus.