The intellect, the rational faculty — what is highest in the human being. For the Stoics νοῦς is close to the TERMruling part and to the cosmic Logos: an individual intellect is a "fragment" (ἀπόσπασμα) of the divine reason diffused throughout the cosmos. Through νοῦς the human being shares in god, and through god in other human beings: the commonality of intellect is the ground of the TERMkinship of rational beings.

SVF I 87 (Zeno on the soul as pneuma); II 879, 885 (νοῦς as part of the world-soul); DL VII 138–139, 156–157; LS 53–54. In Marcus: Med. 2.1; 3.6; 05-27; 05-30 (the mind of the Whole is social, κοινωνικός); 06-40 (to live by the making power of nature → all κατὰ νοῦν); 06-51 (the good of the rational being lies in his own action, ὁ νοῦν ἔχων); 07-30 (εἰσδύεσθαι τὸν νοῦν — "dive with the mind" into what happens and who does it); 07-66 (Socrates did not let his νοῦς sympathize with the affects of the flesh); 08-16 (a change of mind is carried out κατὰ νοῦν τὸν σόν — by your own mind); 08-41 (ἐμποδισμὸς νοῦ — an evil to νοερὰ φύσις; the mind-sphere is untouchable); 08-60 (νοῦς moves unlike an arrow: even cautious and circling, it goes κατ’ εὐθύ to its object); 10-11 (οὐδ’ εἰς νοῦν βάλλεται — others' words and judgements he does not even take into his mind); 10-24 (μήτι κενὸν νοῦ ἐστι; — the first of the three diagnoses of the ruling part); 10-33 (νοῦς καὶ λόγος — the only thing to which movement by its own nature is granted "everywhere": to a cylinder, to water, to fire it is not); 11-01 (ἐὰν νοῦν ὁποσονοῦν ἔχῃ — "if he has any intelligence at all": a small share suffices for a man of forty to have seen all that was and will be κατὰ τὸ ὁμοειδές); 12.26. In Book XII — 12-02 (τὸ ἑαυτοῦ νοερόν: God touches the intellectual only with the intellectual, like by like); 12-03 (νοῦς is set as the third member of the triad and called "properly yours"). And 12-14 (τις νοῦς ἡγεμονικός — the one thing the surge will not carry off: τὸν γὰρ νοῦν οὐ παροίσει). And 12-26 (ὁ ἑκάστου νοῦς θεός — and the human community is a νοῦ κοινωνία); 12-30 (μία νοερὰ ψυχή, and διάνοια "in its own way" stretches toward what is of its kind). In Books I–IV: 03-03, 03-07, 03-16 (νοῦς as the third member of the triad σῶμα / ψυχή / νοῦς, and δόγματα belong to it alone); 04-05 and 04-29 in the form νοερόν.

Marcus frequently uses the substantivised adjective τὸ νοερόν ("the rational / thinking part") as an equivalent of νοῦς — above all in the programmatic 04-04 (the cosmopolis sorites: "Εἰ τὸ νοερὸν ἡμῖν κοινόν…" — "if our rational part is common…"), where νοερόν sounds three times. It is the same faculty as νοῦς, taken from the side of its generic commonality across all rational beings.

In Marcus, νοῦς figures as the inner δαίμων — the guiding genius, the "god within us" (Med. 3.6; 05-27). In passage 02-01 it is precisely νοῦς (and not the narrower ἡγεμονικόν) that is named, because the point is what binds human beings together: their shared rationality as an ontological connection, not as an individual centre of decision. See TERMtheia-apomoira: the formula "sharing in intellect and the divine portion" applies not only to the sage but to every human being.