Abstract
The last part of Chapter 2 and the first part of Chapter 3 of De mundo (392a31-393a8) describe the cosmic layers further below the sphere of the moon, leading down to the very centre of the universe. This section provides a brief overview of the sublunary layers of the four elements (fire, air, water and earth), some of which will be discussed in more detail later in the text.
The two main theses that constitute the reasoning behind this section are (i) continuity throughout the entire cosmos and (ii) the great variety of phenomena and processes within the sublunary domain. The layers are organised from the most active one at the top down to the most passive one at the centre of the universe.
For our author's purpose it is sufficient to demonstrate that there is some relation, some communication among the layers which can later be used by the divine dunamis permeating the entire cosmos.