In Stoic ethics, oikeiôsis (Ancient Greek: οἰκείωσις, Latin: conciliatio) is a technical term variously translated as "appropriation," "orientation," "familiarization," "affinity," "affiliation,"[1] and "endearment.
In his Elements of Ethics (Ἠθικὴ στοιχείωσις), the philosopher Hierocles began his account of oikeiôsis by looking at the beginning of the life of animals.
This is why, according to Hierocles, children are afraid of the dark, because their weak sense of self fears death in the absence of external entities.
[6] Hierocles argued that the impulse of self-preservation arises out of oikeiôsis: "an animal, when it has received the first perception of itself, immediately becomes its own and familiar to itself and to its constitution".
[8] In Hierocles' other ethical work, On Appropriate acts (of which only fragments survive), he outlined a theory of duty based on concentric circles.