Demon, supernatural being, spirit, or force capable of influencing human lives, usually by
evil means. Demons have played a role in the traditions of most religions and also have appeared in mythology and literature.
Exorcism, the practice of expelling demons that possess people or places, has been carried out by many religions, usually
by a person with special authority. The study of demons is called demonology.
The belief in evil spirits and their ability to influence the lives of people dates from
prehistoric times. Many early people believed that spirits occupied all elements of nature. Evil spirits or demons were the
spirits of ancestors who brought harm to living people. Societies that practiced ancestor worship sought to influence the
actions of both good and bad spirits (see Religion: Primitive Religions). Some ancient societies, including those in Egypt
and Babylonia (now Iraq), believed that such spirits were responsible for the functions of the body and that demons caused
specific illnesses.
Spirits and demonic beings became an important part of Hinduism, the religion of India. Hindu
scriptures called the Vedas, composed between about 1500 bc and about 1000 bc, describe a variety of evil beings, including
the asuras and the panis, who harm people and work against the Hindu gods. The word demon originated from an ancient Greek
term, daimon, which referred to beings whose special powers placed them between people and the gods. These beings had the
ability either to improve people's lives or carry out the punishment of the gods.
Basic Christian ideas about demons originated from references to evil beings or unclean spirits
in the Old Testament of the Bible. By the Middle Ages, Christian theology had developed an elaborate hierarchy of angels,
who were associated with God, and fallen angels, or demons, who were led by Satan. Satan himself was considered the original
fallen angel. In most English versions of the Bible, the term demon is translated as devil, and in the New Testament, demon
is identified with an evil spirit (see Angel; Devil).
Islam also developed a complex system of demons. Muslim writings describe a group of evil
beings, called jinn, who cause destruction and preside over places where evil activities take place. The original jinn was
called Iblis, who was cast out by Allah for refusing to worship Adam, the first man.
Demons also have become part of folklore throughout the world. Many of these demons have
peculiar qualities. They include such familiar creatures as vampires, who suck the blood of living victims. Another variety
of demon, the Japanese oni, are said to bring on storms. In Scotland legendary kelpies haunt pools, waiting to drown unwary
travelers. Popular belief in demons and evil spirits has steadily declined since the 1700s.