Editing Zeno of Citium (section)

===Physics===
The [[universe]], in Zeno's view, is [[God]]:{{sfn|Laërtius|1925|loc=§ 148}} a divine reasoning entity, where all the parts belong to the whole.<ref>Sextus Empiricus, ''adv. Math.'' ix. 104, 101; Cicero, ''de Natura Deorum'', ii. 8.</ref>  Into this [[pantheistic]] system he incorporated the physics of [[Heraclitus]]; the universe contains a divine artisan-fire, which foresees everything,<ref name="cicero2">Cicero, ''de Natura Deorum'', ii. 22.</ref> and extending throughout the universe, must produce everything:
<blockquote>Zeno, then, defines nature by saying that it is artistically working fire, which advances by fixed methods to creation. For he maintains that it is the main function of art to create and produce and that what the hand accomplishes in the productions of the arts we employ, is accomplished much more artistically by nature, that is, as I said, by artistically working fire, which is the master of the other arts.<ref name="cicero2"/></blockquote>

This divine fire,<ref name="cicero1"/> or aether,<ref>Cicero, ''Academica'', ii. 41.</ref> is the basis for all activity in the universe,<ref>Cicero, ''de Natura Deorum'', ii. 9, iii. 14.</ref> operating on otherwise passive matter, which neither increases nor diminishes itself.{{sfn|Laërtius|1925|loc=§ 150}} The primary substance in the universe comes from fire, passes through the stage of air, and then becomes water: the thicker portion becoming earth, and the thinner portion becoming air again, and then rarefying back into fire.{{sfn|Laërtius|1925|loc=§ 142, comp. 136}} Individual [[souls]] are part of the same fire as the [[Anima mundi|world-soul]] of the universe.<ref>Cicero, ''Tusculanae Quaestiones'', i. 9, ''de Natura Deorum'', iii. 14; {{harvnb|Laërtius|1925|loc=§ 156}}.</ref> Following Heraclitus, Zeno adopted the view that the universe underwent regular cycles of formation and destruction.<ref>Stobaeus, ''Ecl. Phys.'' i.{{full citation needed|date=September 2021}}</ref>

The nature of the universe is such that it accomplishes what is right and prevents the opposite,<ref name="cicero3">Cicero, ''de Natura Deorum'', i. 14.</ref> and is identified with unconditional [[Destiny|Fate]],{{sfn|Laërtius|1925|loc=§ 88, 148, etc., 156}} while allowing it the free-will attributed to it.<ref name="cicero2"/> According to Zeno's beliefs, "[t]rue happiness" can only be found by obeying natural laws and living in tune with the course of fate.<ref>{{Cite book |last=Caldwell |first=Wallace E. |title=History of the World |last2=Merrill |first2=Edward H. |publisher=The Greystone Press |year=1964 |volume=1 |location=[[United States]] |pages=119}}</ref>