κοινωνικός means "social, communal"; the substantive τὸ κοινωνικόν is "the social element," the feature of rational nature by which the human being exists not for himself but for the whole. In Marcus it is one of the two defining properties of man, inseparable from τὸ λογικόν (the rational): to be rational is to be social, for reason by its nature institutes community (κοινωνία). The proper activity of the ruling part is κοινωνικαὶ πράξεις, "social actions" directed at the common good; these are the true "work of a human being" (ἀνθρώπου ἔργον).

The ontological ground of the social is the unity of the cosmos (one substance, one Logos, one city); the ethical ground is οἰκείωσις, the natural "appropriation" that widens from oneself to one's neighbours and to all rational beings. The opposite of the social is ἀντιπράσσειν, "working against" the whole, which amounts to self-dissolution (see the images cooperation, body-parts).

DL VII (the properties of the sage — κοινωνικός among them); the Stoic οἰκείωσις — Cic. Fin. III (the extension of "appropriation" to others); Off. I (man as a social being); SVF III; LS 57. Background: Aristotle, Pol. I 2 (man as ζῷον πολιτικόν, the political animal). In Marcus, κοινωνικός / τὸ κοινωνικόν runs through the whole corpus — e.g. Med. 2.1 (we are born for cooperation); 05-06 (the three kinds of benefactor; ἔργον κοινωνικόν); 05-16 (the good of a rational being is fellowship, κοινωνία); 05-22 (what does not harm the city does not harm the citizen); 05-29 (to live by the nature of the rational and social animal); 05-30 (the mind of the Whole is social — the ground of our κοινωνία); 06-07 (joy and rest in passing from one social act to another, with the remembrance of God); 06-14 (the hierarchy of value — guard the rational-social soul, cooperate with one's kind); 06-23 (toward human beings behave socially, since they share reason); 06-30 (the one fruit of life — piety and social acts, πράξεις κοινωνικαί); 07-52 (let no one surpass you in κοινωνικόν); 07-55 (τὸ κοινωνικόν — the προηγούμενον in the human constitution); 07-64 (pain corrupts the mind neither as λογική nor as κοινωνική); 07-67 (not a dialectician — then at least free, modest, κοινωνικός, obedient to god); 07-72 (whatever is neither νοερόν nor κοινωνικόν is below the rational-social faculty); 08-02 (the present work — of a rational and κοινωνικοῦ being); 08-07 (ὁρμαί directed to κοινωνικὰ ἔργα alone — the discipline of action); 08-12 (πράξεις κοινωνικὰς ἀποδιδόναι — to rise from sleep to the common work); 09-06 (πρᾶξις κοινωνική — "the present action for the common good": the second member of the triad of disciplines); 09-23 (every πρᾶξις should complete the ζωὴ πολιτική and refer to the κοινωνικὸν τέλος); 09-31 (κοινωνικῶς πρᾶξαι — the social act as the end of ὁρμή and πρᾶξις, κατὰ φύσιν); and passim.

In 05-01 κοινωνικαὶ πράξεις stand at the climax of the morning exhortation: they are not "cheaper" (εὐτελέστεραι) but worthier of zeal than the crafts of the artisan or the money-lover. The term links the discipline of action to the teleology of nature: the "work of a human being" = social action.