The Hesiod's Theogony is not, as is often defined by modern philologists, a simple and banal "literary work". It is a didactic poem of mythological-religious topic and, at the same time, a sacred and initiatory text. It is - with the sole exception of the Homeric poems in the profane field, and of some secret texts handed down by the ancient Mystery Schools in the initiatory sphere - the most ancient mythological-religious text of public domain from archaic Greece. Its content and the precious information that it provides about the origin and nature of the Gods constituted a very important canon for all the later literatures. It was used both in the Hellenic and Roman world, and its reading is still indispensable today for the knowledge of the religious thought of ancient Greece. However, the Hesiodic text is not unique, nor it represents an innovation. It fits into a long tradition, which is mostly an exclusive prerogative of the Mystery Schools linked to the Eleusinian Mother Tradition and to its derivations, which are the Orphic, Pythagorean or Samothracian branches. Who was Hesiod? A poet? A narrator? A priest? An Initiate? Or all these things together?