JMA-PSOS

BigThink published a short story last fall, a dialogue between Anaximander and Anaximenes, his student, about the universe.  In it, the teacher mentions his apeiron, which is the infinite and the unlimited. 

I love what Theophrastos said about him:

Anaximander of Miletos, son of Praxiades, a fellow-citizen and associate of Thales, said that the material cause and first element of things was the Infinite, he being the first to introduce this name of the material cause. He says it is neither water nor any other of the so-called elements, but a substance different from them which is infinite" [apeiron, or ἄπειρον] "from which arise all the heavens and the worlds within them.—Phys, Op. fr. 2 (Dox. p. 476 ; R. P. 16).