One intelligent soul for all. An ascending gradation of ensoulment: among non-rational animals a single TERMsoul is "divided out" (διῄρηται) — one vital nature; among rational beings a single intelligent soul (μία νοερὰ ψυχή) is "parcelled out" (μεμέρισται). Marcus ranks the rational higher: what unites them is not mere life but mind. There follow three physical "ones" that prop the thought by analogy: one earth for all earthy things, one light by which all see, one air all breathe. As the body shares in common elements, so reason shares in a common rational principle.

The ground of sociability. This is not abstract cosmology but the physical basis of DOGMAoikeiōsis: if the rational soul in all is one, then another human being is literally kindred to me in mind, and enmity toward him is a split within a single thing. The thesis is carried straight on in 9.9 (all that is akin strives toward the akin) and rests on the DOGMAunity of the cosmos (cf. 12.30: "There is one light of the sun… There is one intelligent soul, though it seems to be divided"). The governing discipline is desire (the contemplation of nature that yields acceptance of one's place in the whole).