How does Marcus Aurelius describe the parts that make up a human being?

Marcus opens Meditations 2.2 with a question he asks himself as a kind of daily reset: whatever this is that I am, what is it made of. His answer names three things: a little flesh, breath, and the ruling part (Meditations 2.2).

Flesh comes first because it is the most obvious and the least impressive on inspection. Marcus tells himself to look at it as if he were already dying: it is blood and bones and a network, a contexture of nerves, veins, and arteries (Meditations 2.2). Stripped of its surface, the body is plumbing. That is not a complaint about the body so much as a corrective to the weight we give it. We spend enormous energy on how the flesh looks and feels, and Marcus wants to remind himself that this is a strange thing to build an identity around.

Breath is the second part, and Marcus treats it almost as briefly as the flesh. It is air, he says, and not always the same, but every moment sent out and again sucked in (Meditations 2.2). Breath keeps you alive, but it has no character of its own. It comes and goes, indifferent to who you are. In Stoic physics breath (pneuma) is bound up with soul and vital heat, but here Marcus is not giving a lecture in physics. He is stripping the self down to see what is left when you set aside the parts that merely happen to you.

The third part is the one that matters: the ruling part, in Greek the hegemonikon, the seat of judgment and choice. This is where Marcus's real interest lies, and the passage turns on it. He does not just name it, he addresses it directly, almost scolding it: you are an old man, he says, no longer let this be a slave, no longer be pulled by the strings like a puppet to unsocial movements, no longer either be dissatisfied with your present lot, or shrink from the future (Meditations 2.2).

The common misreading is to hear "flesh and breath and the ruling part" as a neutral inventory, as if Marcus were doing anatomy. He is not. The list is a ranking disguised as a description. Flesh and breath are described in a few words each and then set aside. The ruling part gets the weight of the passage, because it is the only part that is up to you. You do not choose your bones or your breathing. You do choose, moment by moment, whether your judgments are sound, whether you act with justice and courage, whether you are pulled like a puppet by other people's opinions or by your own confused desires.

This is the same idea Marcus works through elsewhere in book two, where he notes that death, pain, honor, and dishonor happen equally to good people and bad, which is why none of them can be what makes a life good or bad (Meditations 2.11). If externals cannot make you better or worse, then the part of you that can be better or worse, the ruling part, is where your attention belongs.

What changes if you take this seriously is not that you stop caring for your body or ignore how you feel. It is that you stop mistaking the condition of flesh and breath for the condition of your character. A sprained ankle or a shortness of breath tells you something about your body. It tells you nothing about whether you judged well today. The concrete practice Marcus is modeling here is a short self-audit: notice the flesh, notice the breath, then ask what the ruling part has been doing, whether it has been reasoning clearly or being dragged around by impressions it should have examined first.