At a young age, Marcus Aurelius is chosen to one day ‘assume the purple,’–to become emperor–by Hadrian. Perhaps Hadrian saw something in him, perhaps since he lacked a son of his own, he thought he might be able to cultivate the traits needed to successful rule the Roman empire.

Hadrian set in line a succession plan that involved Hadrian adopting the elderly Antoninus Pius who in turn adopted Marcus Aurelius. All the while, Marcus studied philosophy–he read and thought about what it meant to be a good person.

In 161 AD, after the death of Antoninus, Marcus becomes emperor. We’re told that absolute power corrupts absolutely. Well, now, Marcus had it. And what did he do upon ascending to the throne? His very first decision?

He appointed his step-brother Lucius Verus co-emperor. He was given unlimited, executive power and the first thing Marcus did was share it with someone he was not even technically related to. There was nothing Hadrian’s or Antoninius’s wills that mandated this. Marcus simply did it because he thought it was fair. Because it was the right thing to do.

That’s magnanimity. That’s what Robert Caro means when he says that power doesn’t corrupt, it reveals.