This series was to build on Campbell's idea, first presented in The Hero with a Thousand Faces, that myth evolves over time through four stages:
The Way of the Animal Powers—the myths of Paleolithic hunter-gatherers which focus on shamanism and animal totems. This volume was covered in two parts: Mythologies of the Primitive Hunter-Gatherers and Mythologies of the Great Hunt.
The Way of the Seeded Earth—the myths of Neolithic, agrarian cultures which focus upon a mother goddess and associated fertility rites. This volume was to be covered in five parts, of which three were completed: The Sacrifice, Mythologies of the Primitive Planters: The Northern Americas, and Mythologies of the Primitive Planters: The Middle and Southern Americas. Two additional parts were planned: Mythologies of the Primitive Planters: Africa and South-western Asia and Mythologies of the Primitive Planters: Southern Asia.
The Way of the Celestial Lights—the myths of Bronze Age city-states with pantheons of gods ruling from the heavens, led by a masculine god-king.
The Way of Man—religion and philosophy as it developed after the Axial Age (c. 6th century BC), in which the mythic imagery of previous eras was made consciously metaphorical, reinterpreted as referring to psycho-spiritual, not literal-historical, matters. This transition is evidenced in the East by Buddhism, Vedanta, and philosophical Taoism; and in the West by the Mystery Cults, Platonism, Christianity and Gnosticism.