Oikeiōsis (οἰκείωσις) is the doctrine of "appropriation" or "making-one's-own": every living thing perceives, from birth, its own self and its own constitution as "its own" (οἰκεῖον) and strives for self-preservation. In the rational being this primary self-attachment develops in two directions: (1) inward — toward one's own reason as what is most properly "one's own" (and so virtue is identified with agreement with one's rational nature), and (2) outward — in concentric circles: those close to us, fellow-citizens, the whole of humanity, all rational beings. From a biological drive, in this way, grows the foundation of Stoic cosmopolitanism.

The doctrine goes back to Zeno and is developed by Chrysippus (SVF III 178–189). The classical exposition is in Cic. De fin. III 16–22 and III 62–68; cf. Hierocles, Elementa Ethica, with the famous image of the concentric circles (Stob. IV 27.23 H). In Marcus the doctrine is not formulated explicitly, but pervades the book: Med. 2.1; 3.4; 6.44; 7.55; 9.9; 12.30. See also Sen. Ep. 95.52.

Passage 02-01 is the ethical consequence drawn from oikeiōsis: human beings are TERMkindred to one another not by blood but by reason, and so irritation toward one's neighbour contradicts the structure of "what is one's own." Linked to unity-of-cosmos (the ontological ground of kinship) and to TERMsynergia (its active expression). See also the exercise view-from-above, which unfolds the concentric circles in visual form.