The pagan incubus was a special priest embodying a prophetic spirit who would come in dreams or visions to those who "incubated" overnight in an earth-womb Pit of a temple . The Greeks were known to practice incubation especially in the healing temples of Asklepios and Hygieia. The favorite incubus appeared in the temples of Imhotep. There is suspicion that falsification occurred when the sleeper was a person of political importance; the correct prophecies and advice were conveyed so to benefit the temple.
This custom of incubation was carried into Christianity. It became known as "watching" or "keeping the vigil." It was recommended in times of troublesome decision making that one should "watch and pray" in a church overnight in order to court a vision of guidance. Eventually the incubus was diabolized; and no longer regarded as a guiding angel. The cause for his fall from grace was tales of ancient tradition midnight sexual relationships between incubating women and priests, or incubating men and priestesses. This caused the incubi to be known as spirits of lust. The concept that sexual activity could possess a spiritual nature was completely negated.
Soon it was thought incubi produced children through the demonic version of the Virgin Birth. This originated in a round of name-calling. One early priest Father Ludovico Sinistrari thought the incubus when having intercourse with a woman begot the fetus from his own seed. He added the Holy Mother Church could correct him since this was his personal opinion. Sinistrari called "that damnable heresiarch Martin Luther" a well-known example of a devil-begotten man. Luther seemed no more charitable since he said that all odd-looking children should be destroyed at birth, for they were clearly the offspring of demons.
This argument seemed to rage for centuries. Thomas Aquinas insisted that demons were sterile; therefore the only way the incubus could impregnate a woman was by receiving the seamen from a succubus who had received from a man. Also, aiding in this theory was the idea that demons were able to change their sex at will. Aquinas further asserted that a demon could use seamen lost during a wet dream so a man could be "at one and the same time a virgin and a father."
Here Aquinas contradicted Augustine's biblical interpretation of Genesis 6:4 in which he attempted to prove that fallen angels begot children of mortal women. "The sons of God came in unto the daughters of men, and they bare children to them." Pope Benedict XIV announced, "This passage has reference to devils known as incubi and succubi." The pope declined to settle the demonic conception question, but did state both schools of thought: "Some writers deny that there can be offspring…Others, however, asserting that coitus is possible, maintain that children may result" On that theory, a woman was burned at Carcassonne in 1275 for bearing a child to the devil.
The duration of this argument that lasted decades is too exhaustive to describe here. One might note, however, the Christians certainly handled this situation far differently than their pagan ancestors. In Grecian time men such as Hercules who were born of a god and mortal woman were looked upon as heroes with supernatural powers. They were respected and often revered as champions of the people. But, the church attributed legends of demonic parentage to such historical figures as Robert of Normandy, Alexander the Great, Plato, Scipio Africanus, all the Huns, and all the Cypriots.
Perhaps only possibly reason for this castigation is the Church's attitude toward sex itself. The Christian view that all sexual activity outside of marriage is sinful is directly opposed to the view held by their pagan ancestors. The Greeks and Romans had laws regarding sex and marriage, that is true, but sex was viewed as natural, not sinful. The Greeks accepted the idea that their gods had sex with mortal women. This was viewed as natural because the gods were viewed as having natural tendencies as men. But, where all sex outside of marriage is seen as evil, such persons described as being begotten from immoral relationships can be said to be evil too. Often this suited the purposes of churchmen.