The extirpation of pagan beliefs in the countryside remained a pressing concern among Christian prelates throughout the early Middle Ages. In the sixth century, a bishop in Portugal named Martin of Braga (ca. 520–80) wrote a letter to a neighboring church official in which he lamented the stupidity of sinful countryfolk who venerated demons in the guise of pagan gods. In this letter, Martin explained the origin of the rebel angels, the fall of humankind, and the deception of the demons, who adopted the names of ancient criminals and enticed foolish people to worship them as though they were divine. Even worse, many of those who directed their devotion to the demons were already Christians, who recklessly forsook the sign of the cross for the signs of the Devil.
After God in the beginning had made heaven and earth, he made spiritual creatures, the angels, to stand in God’s sight and praise him in that heavenly home. One of them, made to be an archangel surpassing all others, saw himself radiating such glory that he did not give the honour to his Creator but claimed to be like him. Because of this pride—along with many other angels who supported him—he was thrown out of that heavenly place into this air of ours, which is beneath the heavens. An archangel at first, he then lost his glorious light and became the Devil, dark and horrifying. It was the same with those other angels who had agreed with him and were also thrown out of heaven, losing their own brightness: they were made into demons…
After this fall of the angels, it pleased God to shape man from the mud of the earth…Then, once the Devil saw that man was made to inherit the place in God’s kingdom from which he had fallen, envy led him to persuade man to transgress God’s commandments, and for that offence man was driven out of Paradise into exile in this world of ours, to bear much labour and grief…Humans, once again forgetting the God who had created the world, forsook their Creator to worship creatures. Some adored the sun, some the moon and stars, some fire, some the deep water or water from springs, believing them all not to be made by God for man’s use but to be gods who had come forth on their own.
Then the Devil and his servants, the demons, began showing themselves to humans in various forms, talking to people and trying to get them to offer sacrifices to them high in the mountains and deep in the woods, worshipping them as gods. And they used the names of people who were criminals, people who had spent their lives in all sorts of criminality and law-breaking.
So one demon would claim to be Jupiter, who had been a magus so sunk in incestuous adultery that he took his own sister—whose name was Juno—as his wife, seduced his daughters, Minerva and Venus, and also committed the most disgusting incest with his grandchildren and all his relatives. But another demon named himself Mars, the instigator of discord and conflict. Then another demon, the deceitful deviser of all theft and fraud, decided to call himself Mercury: people who lust as much for profit as this god sacrifice to him when they pass through a crossroads by making mounds of rocks and throwing stones at them. Also, another demon took the name of Saturn for himself: since cruelty was his whole existence, he even ate his own children as they were being born. Another pretended to be Venus, a woman who was a whore and had whored herself not only in countless adulteries but also with Jupiter, her father, and her brother Mars.
See how lost people were in those days when ignorant peasants honoured the demons—sinning grievously—with devices of their own, and then for their own purposes the demons used the language invented by such people, so that they would worship them as gods, offer them sacrifices and imitate the evil deeds of the demons whose names they invoked…The damage that peasants do now, however, does not happen without God’s permission because they have made God angry and do not believe wholeheartedly in the faith of Christ. So fickle are they that they name each day of the week with the name of a demon, saying “the day of Mars,” “of Mercury,” “Jupiter,” “Venus” and “Saturn,” though no day was made by those demons—just by sinners and criminals of the Greek people…
Such is the madness that a person baptized in the faith of Christ does not keep the “Lord’s day,” saying instead that he keeps “Jupiter’s day” and the days “of Venus” and “Saturn,” to whom no day belongs, though in their own countries they were adulterers, magicians, the wicked and the unquiet dead. As I have said, however, stupid people show honour and veneration to the demons under the guise of these names of ours!…
As you can see, all this happens after renouncing the Devil, after you have been baptized. Going back to worshipping demons and evil acts of idolatry, you have betrayed your faith and broken the pact that you had made with God. You have abandoned the sign of the cross that you took in baptism, and you look to different Devil’s signs made with little birds, sneezes and many other things…Likewise, a person who stays with the different spells devised by magicians and sorcerers has discarded the spell of the Holy Creed and the Lord’s Prayer and has trampled upon the faith of Christ because it is not possible to worship God and the Devil together.