Symbolism, Imagery, Allegory
An Expansive Neighborhood
Marcus uses the metaphor of the citizen and the city to anchor human identity in its proper cosmic neighborhood. He shows that there's a kinship not only among all rational creatures, but also between rational created beings and their place of origin: the universe or Whole.
Bear with us here.
Marcus builds this image on the idea that we all have reason in common, and so we understand what we should and should not do (this is called natural law). If that is so, Marcus says, then:
... we are citizens. If so, we share in a constitution. If so, the universe is a kind of community. In what else could one say that the whole human race shares a common constitution? From there, then, this common city, we take our very mind, our reason, our law—from where else? (4.4)
In this case, the common city is the Whole (or the universe), which provides the substance of our bodies and the "spark of divinity" that is our reason. But Marcus also uses the image of the city in a more mundane way, when he speaks of his own citizenship:
As Antoninus, my city and country is Rome: as a human being, it is the world. (6.44.2)
Do No Harm
So the city reflects both macrocosm (the universe) and microcosm (Rome/Earth), and gives Marcus a starting point for his "social acts", as well as the starting point for his allegiance to the gods and reason. Since all rational creatures have a single citizenship, so to speak, Marcus owes his fellow citizens tolerance and compassion. Basically, the idea is that deep down, all rational creatures are the same.
As a subject of the universe, Marcus believes he has to do what is best for the Whole. That means following his fated path and accepting all that comes his way including death. In the end, Marcus knows that the good of the city (or the Whole) must always come first:
What is not harmful to the city does not harm the citizen either. (5.22)
As you can imagine, this is a pretty convenient philosophy for a ruler to have. Does it work for all kinds of people?