The daughter as a goddess originally quite independent of her mother is unthinkable; but what is thinkable, as we shall see, is the original identity of mother and daughter. Persephone’s whole being is summed up in an incident that is at once the story of Demeter’s own sufferings.
Kerényi argues that Kore and Demeter are not two independently evolved goddesses subsequently merged but share an original identity, Persephone’s myth being the internalized drama of Demeter herself.
, Essays on a Science of Mythology: The Myth of the Divine Child and the Mysteries of Eleusis, 1949thesis