The Church in Europe during the Middle Ages came to recognize the existence of vampires and changed it from a pagan folk myth into a creature of the Devil. The vampire, though clearly a thing of evil and a pagan myth, had its believability reinforced by preexisting Christian doctrines such as life after death, the resurrection of the body, and "transubstantiation." This was a concept based on the Last Supper and the dogma of Pope Innocent the III in 1215 A.D., that the "bread and wine" and its equivalent during Christian Communion literally transubstantiated into the actual body and blood of Christ. People who adhered to this belief, and who consumed the blood of Christ, would have little difficulty in believing the corrupted corollary to this -- the drinking of blood by evil demons, namely, vampires.

The Church during the Middle Ages gave credence to the belief in vampires, concluded that it alone had the power to stop vampirism, and then reinforced this position two centuries later in 1489 with its landmark book, Malleus Maleficarum. This work was actually designed to deal with the persecution of witches, but it could be applied to evil vampires as well. Unfortunately many innocent people fell victim to this document, and were tortured and executed for no good reason whatsoever. This book, known as The Hammer Against Witches in English, was used to help identify and persecute people who were supposedly in league with the Devil.

Two centuries after this, evidence that the Church still clung to a belief in vampires was found in the writing of the noted theologian Leo Allatius. As a Church scholar he studied the vrykolakas, the Greeks' concept of the vampire. In his 1645 work called On the Current Opinions of Certain Greeks, he concluded that vampires were often the result of excommunication. Proof of their vampirism is that the body does not decay, indicating that it cannot leave this earthly plane. A swollen body was also evidence of possible vampirism. As some bodies might not decay rapidly due to the type of chemicals in the soil or the cold air temperature, and since bodily swelling was the result of naturally produced gasses in a corpse, many a dead man was wrongly presumed to be a vampire. Oddly enough, incorruptibility --the failure of the dead body to decay -- was also a sign of holiness, even evidence of saintliness. The difference was that a vampire did not totally decay but did become grotesque in form with discoloration and bloating, while a holy body remained almost perfectly intact as if still alive. Also, vampires smelled bad during the lack of decay, whereas sanctified bodies did not. (Remember, you needed garlic to overcome the smell of the vampire's corrupting but non-decomposed, undead body.)

Furthermore, it was a common belief of early Greek Christians that a priest or bishop upon excommunicating an evil-doer could also prevent the sinner's body from decomposing, hence the soul would not be free to go to heaven and was left to dwell on earth until it received a pardon for its sins. In the western Church this belief was apparently also held. There was the case of the Archbishop of Bremen in the 10th century, St. Libentius. He was said to have excommunicated some pirates; the body of one of them was allegedly discovered many years later still undecomposed. It apparently required a pardon of its sins by a bishop before its body would dissolve to ashes -- so it was believed. The clergy thus had the power to make or break possible vampires through excommunication and absolution.

Leo Allatius may have been one of the first scholars to declare officially that vampires were under the power of the Devil and that they prowled at night.

Proof of the Church's power over vampires (and hence the power of the crucifix or holy cross to scare off vampires -- although more modern vampires appear to be less susceptible to this) dates all the way back, at least, to Medieval England. A writer named William of Newburgh discussed the case of a man who died in the 12th century A.D. Supposedly he rose from the dead to torment his wife. After causing much consternation with the local villagers and clergy, the bishop of the region pardoned the corpse in writing for all his past sins. The grave was opened and the actual written pardon was placed over the body of the "vampire." The people were surprised -- or maybe not -- to see the body was still in good condition without signs of decay, sure proof of vampirism. But fortunately for everyone, once the pardon was placed in the grave, the vampire visited no more. Note that this method of dispelling the vampire with an official Church document was remarkably more civil and legalistic than the ordinary way peasants would dispense with a vampire found in the grave -- by burning the corpse, ripping out its heart, chopping off its head, or giving it the old wooden stake through the heart.

In the early 1700s the Sorbonne university in Paris formally opposed the all too common practice in popular culture of mutilating corpses to prevent the dead from becoming vampires. The Sorbonne (which the renowned writer Voltaire had once been shocked to discover actually debated the legitimacy of the mythological vampire) finally took the apparently radical position at that time that the mutilation of corpses suspected of vampirism was a practice based on irrational superstitions.

The belief in vampires, however, did not go without intelligent criticism. Dom Augustine Calmet, a French Benedictine monk, actually wrote a book in 1746 which dared to question the existence of vampires, called A Treatise on Apparitions, Spirits and Vampires a.k.a. The Phantom World. Calmet challenged the rampant vampire superstitions of the day and required proof before acceptance of a belief. He especially doubted that vampires could perform superhuman tasks, such as rising from the dead. He also analyzed and critiqued the supposed vampire epidemics throughout Europe, questioning their basis in reality.

Eventually the centuries of ignorance and superstition gave way to the Age of Reason and Enlightenment and the rise of the scientific method. Eventually medical science was able to prove that plagues, such as the Black Death, were not spread by evil, metaphysical vampires but had a very physical, although microscopic, biological basis.