Symbolism, Imagery, Allegory
A Chay-Chay-Chaaaaaiiiinn of Being
Marcus frequently uses the image of the scala naturae or "ladder of nature" to explain the relationship between all created things and their creator. It's pretty much equivalent to the Great Chain of Being you have heard about in your Shakespeare class.
Marcus brings the scala into his writing to flesh out the idea of community that is central to his thinking about humans' purpose on earth:
It has long been shown that we are born for community—or was it not clear that inferior creatures are made in the interest of the superior, and the superior in the interest of each other? But animate is superior to inanimate, and rational to the merely animate. (5.16)
So community for Marcus is not that warm, fuzzy sense of neighborhood that we have today. For him, it's a hierarchical structure that strictly defines who is under the thumb of whom in the great scheme of things.
In the Lap of the Gods, But Sliding Down the Ladder
Yet this structure makes it easy for Marcus to sketch out his duty and purpose in the universe. Since he is more kin to the gods than to, say, a rock, he understands that he must "do the work of a man," which is to be morally upright and concerned for the health of the "city" (which can also mean the "world" or "universe) where he lives.
Marcus also sees this kindred feeling working at the highest rungs of the ladder, in the realm of the gods:
Among yet higher things there exists sort of unity even at a distance, as with the stars. Thus the upper reaches of the scale of being can effect fellow-feeling even when members are far apart. (9.9.2)
But not all is well on the scala in Marcus's day. Our emperor grumbles about the lack of natural kinship between creatures of reason around him—perhaps because so many of his colleagues refuse to obey their directing minds. He worries that in the end, only the lower creatures will have it right—they can't help but show some natural love for all of their kind, since they're all suffering together.