Marcus Aurelius is the only philosopher in this codex who never intended you to read him. Meditations — its Greek title is Ta eis heauton, literally "Things to himself" — was a private journal kept across the years of his reign, much of it composed in camp during the Marcomannic Wars on the Danube frontier. He referred to it as hypomnemata, "notes," and he was emperor of Rome at the time. The fact that we possess it at all is a series of lucky accidents.
He was born to a wealthy but not imperial family in 121 CE, adopted (via Antoninus Pius) into the imperial succession by Hadrian, and ruled from 161 to his death in 180. The reign was almost continuously taxed by war (Parthia, the Marcomannic frontier), plague (the Antonine Plague, by some modern estimates several percent of the empire's population, with regional figures higher), and the personal griefs of someone who outlived most of his children. He was trained in philosophy from boyhood by Junius Rusticus, who introduced him to Epictetus's Discourses. Marcus regarded Epictetus as his most important teacher and quotes him constantly.
Meditations is structurally unlike any other surviving Stoic work. It has no argument, no audience, no developed theory. It returns again and again to the same themes — the dichotomy of control, the view from above, premeditation of adversity, the imminence of death — because Marcus is writing himself back into practice, day after day, with the discipline of a man who knows he will lose it if he does not. The book reads like notes from a long conversation with himself.
He is the Stoic most useful for someone whose philosophy is intellectually clear but practically slipping. He is not introducing the doctrine; he is rehearsing it. The repetition, which would be a flaw in a treatise, is the entire point in a journal. The Meditations is, in a literal sense, the longest documented attempt by one person to live the Stoic life on the page. That is its value. It is also its measure.