Folk religion refers to the indigenous beliefs held all over the world, especially prior to the introduction of large, organized religions like Christianity and secular movements like science and reason. Many people still follow indigenous religions, particularly in parts of South America, Africa, China, and Southeast Asia. The largest folk religion in the world is the Chinese folk religion, which has an estimated 400 million followers worldwide, about 6.6% of the global population. Folk religions have even more followers than Buddhism or Judaism, claiming about 10% of the world population in total. Only Christianity, Islam, and Hinduism have more adherents.
Despite being followed by groups separated by many thousands of miles, many aspects of folk religion have features in common. Folk religion is heavily steeped in superstition and magic, especially sympathetic magic, the notion that like influences like, even if they are not causally connected in any immediately obvious way. For instance, the idea that the movements of the stars and planets somehow influence or portend events or tendencies on the human scale. The popularity of astrology and psychics shows us that folk religion still exists, even in the Western world.
There are several common features and/or examples of folk religion. These include theophanies, or appearances of a god or spirit to a human, also known as divine disclosure; perceptions of religious imagery in natural phenomena; ancestor worship; the use of amulets and other magical objects; animism; belief in traditional systems of magic or superstition; blessing animals, individuals, and/or crops; and rituals to ward off demons, witchcraft, the Evil Eye, etc. A classic book that describes tens of thousands of folk religious traditions and their parallels is The Golden Bough by Sir James Frazier.
Those aware of the features of folk religions can easily see how they have been absorbed into modern mega-religions like Christianity and Islam. For instance, Christmas marked a Pagan feast day prior to the advent of Jesus' birth. Then it was known as the Winter Solstice. The symbolic consumption of Jesus' body and blood during Mass is an example of sympathetic magic, whereby he who consumes the magical substance is imbued with some of the sanctity that comes from the divine persona. There are countless other examples.
In some places of the world, there are deliberate revivals of folk religions, which are sometimes seen as more genuine -- and certainly older -- than new arrivals such as Christianity. These places include Norway (Odinism), the Baltic states, Celtic countries, Finland, Germany, Greece, and various localities throughout Russia.
