The Devil is known by many names, including Satan, Lucifer, Mephistopheles, Beelzebub, The Evil One, and The Prince of Darkness. According to the Bible, he was originally one of God's foremost angels, but pride and envy caused him to revolt and commence his evil activities. One of his main activities is to try to tempt people away from God, convert them into his own worshipers, and encourage them to sin.
He is usually depicted as a large repulsive two-legged being. He may have horns, fangs, cloven hooves, a tail, scaly skin, and red eyes. Since he was originally an angel, he is sometimes depicted with wings. Medieval artists often gave him the legs and hindquarters of a goat. But no one knows what he really looks like, because he has the ability to disguise himself by magically taking on any appearance he chooses, or by fading into invisibility. In fact many modern Christians regard him as a supernatural spirit rather than a physical being.
People often ask why God allows him to pursue his evil activities. One possible answer is that God doesn't have full control over his former angel. Another answer is that God permits him to tempt people in order to test their faith and devotion. But the first answer implies that God isn't truly all-powerful. And the second answer makes God the ultimate tempter, and the ultimate cause of much of the pain and suffering that people experience.
The Devil is sometimes identified with the serpent that tempted Eve in the Garden of Eden. But he makes his first open appearance in the Book of Job, where he is an angel named Satan living at the Court of Heaven. Acting as an advisor, he tells God that humans only obey his commandments because they are rewarded for doing it. To test this assertion, God gives him permission to inflict severe and undeserved suffering on a devout man named Job. Although Job doesn't understand why he is punished, he never relinquishes his faith in God.
In the Book of Job, Satan is still part of the heavenly court, and he never makes an open break with God. But in later Jewish writings, especially in apocryphal literature outside the Old Testament, he develops into a full-fledged fallen angel. And by the period of the New Testament, he has become the true Evil One.
As Christianity grew and spread, so did belief in the Devil. During the Middle Ages he was often depicted in paintings as a half-man half-beast, but in popular stories he could disguise himself as a black cat or a toad. He was blamed for illness, accidents, immoral behavior, crop failures, and natural disasters.
Belief in the devil was especially strong during the witch crazes of the sixteenth and seventeenth centuries. During this period thousands of people were accused of being his helpers, and many of them were tortured and killed.
In Islamic societies the Devil goes by the names Iblis and Shaitan. According to the Qur'an (Koran), he is a jinni (genie) who refused to obey Allah and was thrown out of Paradise. To hinder his evil activities, angels repeatedly throw shooting stars down at him.
Today many doubt that the Devil really exists. They say that biblical stories such as the punishment of Job are allegories. Another popular view is that Satan is merely a personification of the evil within our own selves, an imaginary being that we can conveniently blame for our own bad behavior.