A question, not a statement. Πῶς ἑαυτῷ χρῆται τὸ TERMἡγεμονικόν; — "how is the ruling part using itself?" The reflexive is the whole content: the question is not how the mind disposes of things but how it deals with itself. Cf. 12.1 and 12.3, where the same is named as the only thing properly one's own.

The valuation is set down at once. ἐν γὰρ τούτῳ τὸ πᾶν ἐστι — "for in this is the whole." Not "the main thing," not "the most important": everything. That is why the entry is short: if everything is here, there is nothing to add.

And the sharpest move in the book. τὰ δὲ λοιπὰ ἢ TERMπροαιρετικά ἐστιν ἢ ἀπροαίρετα, νεκρὰ καὶ καπνός. Ordinarily the dichotomy divides: what is in our power matters, what is outside it is indifferent. Here Marcus names both sides and throws them out together — what falls under choice and what does not, if it is not the mind itself in its relation to itself, is "dead stuff and smoke." The distinction on which the whole school rests turns out to be drawn inside what is in one stroke declared inessential.

A word that ties the entry to its neighbours. καπνός, "smoke": the same word in 12.27 (καπνὸς καὶ σποδὸς καὶ μῦθος), and the cognate τῦφος in 12.24 and 12.27. Toward the end of the book, smoke becomes the running name for everything that is not the ruling part. The governing discipline is assent.