Stoicheia are the four first principles of ancient cosmology: earth (γῆ), water (ὕδωρ), air (ἀήρ), fire (πῦρ). The Stoics take over the Aristotelian four-element system and incorporate it into their physics: the two "active" elements (fire and air) form the subtle TERMpneuma; the two "passive" elements (earth and water) form dense matter. The cosmos is in constant cyclical transformation among the elements; that cycle is itself the existence of the cosmos as a living whole.

SVF II 413–425 (the doctrine of the elements); II 580–632 (pneuma as a mixture of the active elements); DL VII 134–137; LS 47. The Aristotelian background: De gen. et corr. II 2–4. In Marcus: Med. 2.3; 2.17; 4.46; 6.17; 7.50; 12.30.

In 02-03 stoicheia appear in the physical argument for the preservation of the cosmos: "just as the changes of the TERMelements preserve the cosmos, so too do the changes of composite bodies." The logic: what looks like destruction at the level of a particular thing (συγκρίμα — a compound body) is, at the level of the whole, a necessary link in its self-reproduction. The ethical inference: the death of an individual is not a "loss" for the nature of the whole, but the whole's own normal mode of being. See TERMmetabole (the doctrine of transformation) and unity-of-cosmos (the ontological whole).