Occidental Mythology is a systematic and fascinating comparison of the themes that underlie the art, worship, and literature of the western world. The Masks of God is a four-volume study of world religion and myth that stands as one of Joseph Campbell's masterworks. On completing it, he wrote:

"Its main result for me has been the confirmation of a thought I have long and faithfully entertained: of the unity of the race of man, not only in its biology, but also in its spiritual history, which has everywhere unfolded in the manner of a single symphony, with its themes announced, developed, amplified and turned about, distorted, reasserted, and today, in a grand fortissimo of all sections sounding together, irrestibly advancing to some kind of mighty climax, out of which the next great movement will emerge."