ultimum et altissimum atque undique circumfusum et extremum omnia cingentem atque complectentem ardorem, qui aether nominetur, certissimum deum iudicat
Cicero reports the Stoic (Chrysippean) doctrine that the all-encircling, highest fiery element—named aether—is identified as the most certain god, establishing the term’s foundational theological valence.
, De Natura Deorum (On the Nature of the Gods), -45thesis