One of the most important ecclesiastical documents of the Middle Ages was the Canon Episcopi, ca. 900, which defined witchcraft as Devil-worship but declared it to be nothing more than a foolish delusion.
The origin of the canon is unknown. When it was made public at the beginning of the 10th century by Regino of Prüm, Abbot of Treves, it was erroneously presented as an ancient authority dating back to the fourth century. Around 1140, the Italian monk, Gratian, incorporated
the Canon Episcopi into his authoritative text of canon law, the Concordance of Discordant Canons (usually called the Decretum). Thus the Episcopi became entrenched in the highest canonical law.
The Canon Episcopi denied that witches had the ability to fly through the air and metamorphose themselves into animals and birds. Whoever was “so stupid and foolish” as to believe such fantastic tales was an infidel. While such physical feats were impossible, the canon acknowledged that they could be accomplished in spirit.
The Canon Episcopi presented a dilemma for the demonologists of the 12th century and later, who accepted the physical reality of metamorphosis and transvection. Convoluted theories were put forth in order to skirt the Canon Episcopi. It was reasoned that, even if witches flew with Diana and demons in spirit or imagination only, they were just as guilty as if they had done so in the flesh.
It was then easy to propose that all heretics (including witches) were guilty of having pacts with the Devil just by virtue of being heretics.
With its portrayal of hordes of women riding upon beasts through the air at night, following their goddess Diana, the Canon Episcopi helped promote the idea of the demonical sabbat, the descriptions of which became increasing lurid in the writings of demonologists.
The text of the Canon Episcopi is as follows:
Bishops and their officials must labor with all their strength to uproot thoroughly from their parishes the pernicious art of sorcery and malefice invented by the Devil, and if they find a man or woman follower of this wickedness to eject them foully disgraced from their parishes.
For the Apostle says, “A man that is a heretic after the first and second admonition avoid.” Those are held captive by the Devil who, leaving their creator, seek the aid of the Devil. And so Holy Church must be cleansed of this pest. It is also not to be omitted that some wicked
women, perverted by the Devil, seduced by illusions and 50 Canewdon Witches phantasms of demons, believe and profess themselves,
in the hours of the night, to ride upon certain beasts with Diana, the goddess of pagans, and an innumerable a multitude of women, and in the silence of the dead of the night to traverse great spaces of earth, and to obey her commands as of their mistress, and to be summoned
to her service on certain nights. But I wish it were they alone who perished in their faithlessness and did not draw many with them into the destruction of infidelity. For an innumerable multitude, deceived by this false opinion, believe this to be true, and so believing, wander
from the right faith and are involved in the error of the pagans when they think that there is anything of divinity or power except the one God. Wherefore the priests throughout their churches should preach with all the insistence to the people that they may know this to be in every way false and that such phantasms are imposed on the minds of infidels and not by the divine but by the malignant spirit. Thus Satan himself, who transfigures himself into an angel of light, when he has captured the mind of a miserable woman and has subjugated her to
himself by infidelity and incredulity, immediately transforms himself into the species and similitudes of different personages and deluding the mind which he holds captive and exhibiting things, joyful or mournful, and persons, known or unknown, leads it through devious ways, and while the spirit alone endures this, the faithless mind thinks these things happen not in the spirit but in the body. Who is there that is not led out of himself in dreams and nocturnal visions, and sees much when sleeping which he has never seen waking? Who is so stupid and foolish as to think that all these things which are only done in spirit happen in the body, when the Prophet Ezekiel saw visions of the Lord in spirit and not in the body, and the Apostle John saw and heard the mysteries of the Apocalypse in the spirit and not in the body, as he himself says “I was in the spirit”? And Paul does not dare to say that he was rapt in the body. It is therefore to be proclaimed publicly to all that whoever believes such things or similar to these loses the faith, and he who has not the right faith in God is not of God but of him in whom he believes, that is, of the Devil. For of our Lord it is written “All things were made by Him.”
Whoever, therefore, believes that anything can be made, or that any creature can be changed to better or to worse or be transformed into another species or similitude, except by the Creator himself who made everything and through whom all things were made, is beyond doubt an infidel.
By the mid-15th century, inquisitors and demonologists had begun to dismiss the Canon Episcopi. Its influence, however, lingered for at least another 200 years.