The inner realm is the physical realm, composed of the four Platonic elements: Earth, Water, Air, and Fire. These are the basest realms, comprised primarily of matter with very little spiritual essence. However, these realms are still important to occultists because they are the realms we can most easily comprehend and with which we can most easily rate. One must understand their physical nature before he can hope to elevate himself beyond it.
Nature of The RealmThe Physical realms are considered both material and perishable. Material things do not last forever, and they are frequently subject to compositing and/or mutation into new forms.
Rarified Elements vs. Composite Physical MaterialFurthermore, even these base realms function at a higher level than what we generally consider physical reality. Rainwater is not the same as the element of Water, and a match flame is not pure elemental Fire. Everything that we can physically interact with is a composite of elements, comprised of elemental combinations.
Hence, even the realm of earth, the basest of the Terrestrial realms, is still more pure, more rarefied than the physical soil beneath our feet or the flesh from which we are made.
Earth, Water, Air and FireThe Terrestrial realms are ordered in a scientific fashion: through the application of heat (Fire), solids (Earth) can transform into liquids (Water), which can in turn evaporate into the air (Air). Fire, being the catalyst and strongly associated with the divine light, is then naturally placed at the top of this hierarchy.