In 'An Introduction to Mythology', originally published in the 1921, Spence presented a comprehensive overview of traditional forms of narrative that, for our primitive ancestors, served as religion and science. Besides recounting tales from around the world, Spence explained the many differences in primitive and modern worldviews. According to Spence, themes such as animism, while now almost absent from out thinking, are still enlightening to us in modern times: "just as fossil animals and plants have their living representatives to-day, so do ideas and conceptions representing this petrified form of religion and science still flourish in our present-day superstitions and our present-day faiths." Spence's An Introduction to Mythology provides a sweeping view of worldwide mythological themes from a scholar of the overlooked and intriguing.

Scottish writer Lewis Spence (1874-1955) was a respected authority on worldwide myths, legends, folklore, and occult subjects, and wrote more than forty books.