Genealogy in Hesiod's Theogony
Progression and Expansion
But the origin isn’t really “nothing.” Prior to the coming into being of Chaos and Gaia there “was” some original, apparently static condition. In later terms, instead of thinking of it as nothing, we might call it a condition of pure potentiality, even a state of pure being, a state however, whatever it was, that could not be known until its constituent elements emerged into a state of becoming
Divisions
When the separation is made between Chaos and Earth, these two entities generate separate lines of progeny, the members of which never intermarry. Their separation from each other is represented on Genealogical Chart #1 above by the left-hand set of vertical dashes. The contrast between them has been called that between Unform and Form.
On the one hand, the lineage of Chaos, which is without substance and without form, contains entities that exist but are intangible and invisible: Darkness, Night, and their progeny, Brilliance, Day, etc. They are something like spaces in which creatures with substance can be seen and grasped. And Night then without Eros produces states which can exist within substantial living beings but which have no separate identity or existence apart from what they can achieve by coming to be in other living things. The children of Eris are conditions of pain that can only exist in other creatures, especially humans.
Form, on the other hand, in its initial emergence out of pure potentiality, is present within Earth, but she herself is the principal of substance – the stuff out of which everything else that is substantial comes to be. She contains within herself, however, principles of form, Ouranos (Sky), Ourea (Mountains), and Pontos (Sea).
Along with Earth, all these together may be considered the first order of deities, the order of elemental gods that become the elements of all matter. Sky and Sea in turn, in union with Earth, generate beings that have both substance and form. From Earth and Sky are born the Titans (see Genealogical Chart #2 above).
The Titans, the second order of deities,are intelligible entities that have the power to generate but are more like attributes of fully developed creatures than creatures themselves. From their names, with the exception of Okeanos (Ocean), we understand them to be abstract powers rather than creatures with identifiable shapes that can be represented in art as having “bodies.” And from these “powers” or “attributes” the third generation is born.