structural:summarization, information:highlighting
Cosmology

Firstly, they were preoccupied with the mystery of the cosmic matter—what was the basic substance of the universe? Anaximander suggested apeiron (limitless), which hints, as Aristotle analyzed, there is no beginning and no end to it, both chronologically and within the space. Anaximenes placed aêr (air) as the primary principle, probably after realizing the importance of air to life and/or the need to explain various observable changes. Heraclitus, also seeking to address the issue of the ever changing world, placed fire as the primary principle of the universe, that transforms to water and earth to produce the universe. Ever-transforming nature is summarized by Heraclitus' axiom panta rhei (everything is in a state of flux). Parmenides suggested two ever-lasting primary building blocs, night and day, which together form the universe. Empedocles increased the building blocks to four and named them roots, while also adding Love and Strife, to serve as the driving force for the roots to mingle. Anaxagoras extended even more the plurality of Empedocles, claiming everything is in everything, myriads of substances were mixing among each other except one, Nous (mind) that orchestrates everything—but did not attribute divine characteristics to Nous. Leucippus and Democritus asserted the universe consists of atoms and void, while the motion of atoms is responsible for the changes we observe.