January 25, 2020:
Joseph Campbell took it all back.
His early work The Hero With a Thousand Faces is too often cited as a model on which fictional narratives can be reliably based, like a coloring book or a recipe collection or a set of knitting patterns. Structure your narrative to follow The Hero's Journey, your work will resonate with consumers. We may have George Lucas to blame, although I think Luke Skywalker's story arc resembles Campbell's monomyth only if you do violence to both. Regardless where it originates, you'll find The Hero With a Thousand Faces cited as expert advice in writing classes, manuals of game design, screenwriting seminars, and Novel Writing for Dummies as an appropriate or even necessary structural model for successful plot development.
Which is irrational on its own, but also ironic considering Campbell himself in his mature work The Masks of God disavowed The Hero With a Thousand Faces not just emphatically but in tones of near triumph.
The Hero With a Thousand Faces presents a Jungian problematic: the monomyth is identical worldwide because it reflects universal structures of the collective unconscious. The Masks of God is diffusionist: cultures widely separated over geography and time present similar myths because those myths were disseminated from areas Campbell terms "mythogenic zones", while inevitably adapted to local conditions. The Hero With a Thousand Faces is ahistorical, The Masks of God is historicist. The Hero With a Thousand Faces's Jungian problematic owes more to the Golden Dawn than the scientific method; The Masks of God is based in the anthropological and archaeological record as both evolved over time. In the preface to The Masks of God Campbell cites Chinese wheat discovered in ancient coastal settlements in Chile to demonstrate that migrations over vast difficulties happened in real history, probably many times, bringing with them the idea of pyramids to Mezoamerica.
The Hero With a Thousand Faces is Campbell's first work, an immature incunabulum in his later corpus. The Masks of God is his mature statement.
The Hero With a Thousand Faces should not be taken seriously.