On the night of the 21st of August 1879 the Virgin Mary flanked by St Joseph and a bishop thought to be St John the Evangelist and an altar with a lamb and cross on it allegedly appeared on the gable wall of the Parish Church of Knock for a few hours. Fifteen people witnessed the vision including a child of five (page 60, The Evidence for Visions of the Virgin Mary). Witness statements were published in a highly altered and edited form that differed hugely from the real ones the witnesses made. That witnesses didn't do the slightest thing about the lies speaks strongly against them as honest people.

Pious fraud means a hoax engineered to make people better followers of a religion. The Catholic conscience excuses such conduct. It is thought that though it's a sin to fraud it is not a sin when you have no choice but to do something to stop people going to suffer everlasting damnation through not being believing and faithful Catholics. It is still wrong but you are not culpable for you have no choice.
The evidence for pious fraud
The evidence for pious fraud is the contention of central apparition witness, Mary Beirne, that the apparition came to show that Archdeacon Cavanagh was a very holy man (page 165, Knock The Virgin's Apparition in Nineteenth Century Ireland). The apparition depicted Mary to whom Cavanagh was extremely devoted and St Joseph and a bishop and a Eucharistic altar and a lamb - all symbols that indicate approval for the priesthood and indicating that priests must be respected.
It is mad to think the vision can be read as anti-clerical or supportive of the priest's critics.
The notion that Cavanagh would not have thought of getting somebody to make a vision of St John is inconclusive for the bishop sounds more like St Patrick. The vision is just what somebody trying to make a successful shrine would create for the Irish had great devotion to the Eucharist, St Joseph and the Blessed Virgin and St Patrick. The witnesses choosing to think it was John was not something the Archdeacon could control.
And why did the witnesses think the bishop was John? Because Mary Beirne noticed how the image resembled the statue of St John she saw in Lecanvey near Westport. She was the one who decided it was John. The third figure appeared to be that of St, John the Evangelist ; I do not know, only thought so, except the fact that at one time I saw a statue at the chapel of Lekanvey, near Westport, County Mayo, very much resembling the figure which stood now before me in group. Cavanagh would have been familiar with the statue for he ministered for years in Westport. And Mary Beirne was a friend of his...
Dominick Beirne declared, "The reason I had for calling the third figure St. John is because some saw his statue or his likeness at Lekanvey parish chapel."
Did the Archdeacon have the vision rigged so that Mary Beirne would recognise the bishop as John?
Margaret Beirne was certain of the statue. In her deposition, the following is squeezed in around her signature as if the priest didn't want to put it in. It was obviously important to her that he put it in. "The reason I knew it was St John was because I saw a statue of him at Lecanvey chapel."
Margaret and Mary Beirne had to have been certain otherwise witnesses would have identified it as St Patrick even if they said it was John. They would only agree with them if they gave a solidly good reason. There is no evidence at all that the assertion of some that there was no such statue at Lecanvey is to be even considered. Nobody claimed that at the time. For later supporters of Knock, if a connection was made between the vision and the statue, there might have been a need to downplay the report of the statue in Lecanvey. It was feared the hoaxer copied the image of the statue and had got his information about the statue from the Archdeacon who had ministered before it. It was feared it could show up the Archdeacon's involvement or possible involvement.
Page 26 of Margaret Anna Cusack, states that the Archdeacon had been threatened and an inhabitant of the village had been appointed to cut his ears off but this plan was thwarted by the apparition. The same page tells us the apparition enhanced the reverence of the people towards him. In shrine supporter William Coyne's book, Venerable Archdeacon Cavanagh (Roscommon, 1953) we learn "It was resolved ... to have his ears cut off. However before the date fixed for the sacrilegious act the extraordinary events of the 21 August 1879 (the apparition) had occurred at Knock. There was a complete change ... even the hardest of hearts...regarded it as a direct sign through Our Lady that a crime of the kind contemplated was a desecration" (page 82-84).
Tom Jennings, Ballyhowley, Knock wrote a book called The Story of Knock which also said that the night chosen to give the priest a lesson by hacking off his ears was the night of 21 August 1879! The night of the apparition.
In the latest version of Venerable Archdeacon Cavanagh we read that Cavanagh was to be subjected to a number of threats before having the ears cut off. A member of those terrorists who lived near Knock if not in Knock was strenuously opposed to the impending maltreatment of the priest and was overruled and warned that he would die if he warned the priest. But the decision was leaked nevertheless and the parish denounced the evil plan. A support group was set up who vowed to protect their priest no matter what and were resolved to attack anybody who would attempt violence against him. This version also states that the night of the apparition was to be the night chosen for the attack on the priest (page 74). Cavanagh then knew of what was planned for him.
We see from this that there are more problems.
Why was the priest alone in the cottage that night? His housekeeper, Mary McLoughlin even went out visiting with not a care in the world.
Where were the men who were supposed to be guarding the priest?
Did the protecting the priest no matter what stretch as far as orchestrating a fake apparition or helping the priest to do it?
There is no evidence that Cavanagh was in his cottage when the apparition was first seen.
The witnesses were at the Campbell cottage when they supposedly left the apparition on its own at the gable. They went back and it was gone. There is no evidence that Cavanagh was in his cottage at that point. He could have left to set up the vision. He could have went back when the coast was clear to take his tricks away. The magic lantern being turned off would have been enough to make the people think the apparition had vanished.   Hearsay is not much good but rumours did appear (source Kevin Rockett) that somebody sold the priest a magic lantern.
After the apparition, the priests who investigated it went on the platform at Aghamore near Knock on October 26 1879. This was during a meeting to condemn clergymen hostile to the Land League. Cavanagh was completely opposed to the Land League. The priests of course went to uphold such opposition. The priests themselves then had a reason to want the evidence for the apparition which enhanced the authority and safety of Cavanagh to be convincing - they had the power to manipulate the witnesses and leave out anything disturbing from the record of the testimonies. They had the power to make the witnesses agree. This can be done by asking questions in such a way that the witnesses are led to think they had witnessed things they never seen at all. This would be leading the witnesses. Therapists are not allowed to use leading questions for they put things into the heads of the patients. The site was never examined for evidence of fraud so they didn't do their job as well as one would expect. And they probably didn't want to either . . .
Did the Archdeacon orchestrate a Pious Fraud?
Fraud is possible.
Did this have Mc Loughlin his housekeeper visit the Beirne's who lived near the Church to keep them out of the way until the hoax was set up? She seems to have lied that she saw the vision on the way to their house. She never mentioned it during the time she was there indicating that there was nothing that obviously supernatural about it if she did see something.
The Archdeacon has no alibi for the time of the appearance of the vision or its vanishing.
Mary McLoughlin retired for the night early probably at his request. He needed her out of the way so he could venture out and end the vision.
Mrs Campbell was found at her front door after having ventured out of her deathbed to see the vision. The witnesses ran to her aid. When they went back to the gable it was in darkness and the vision was gone. There is no mention of the Archdeacon being called to spiritually assist her though he was a close neighbour. Where was he? His being in bed was no excuse.
Had this distraction not happened the lantern or projector would have went off anyway. The vision going away when there was nobody around only added to the mystery.
That night the Archdeacon's enemies planned to attack him and cut off his ears. This was averted by the apparition story. What perfect timing! The Archdeacon knew the attack was about to happen. Yet he was on his own in his cottage that evening. Why was he so confident he would not be attacked? Maybe there is nothing to fear when a faked apparition for diversion is on the cards.
A witness, his housekeeper, went to tell him about the vision at the gable and he told her he didn't believe it and would not go to the gable. The trouble is he had a clear view of the gable. The light should have shone in his back windows. He was pretending not to know anything about it.
Mary Beirne said in the 1930's that he dismissed the story saying it was a reflection from a stained glass window at the gable.
The next day he had to be informed about the apparition on the way to say Mass and said he had forgotten that he had heard about it from the housekeeper (page 9, The Apparition at Knock). Mary McLoughlin his housekeeper testified that this was so (page 23, The Apparition at Knock). Again he was pretending.
He said to a reporter after that he did not go to the gable in case people would say he had something to do with faking the alleged apparition. That is like the person who steals your car saying they never went near your area that night in case people would say they were out to steal something. It indicates guilt.
He at least pretended to believe all the miracle reports of healings. He kept a diary of them. He would have known from Lourdes that not all healings are authentic or supernatural. He didn't care - all that mattered was making the apparition popular.
The housekeeper presumably got permission from him to go and visit Beirne's house. It was while she was out that she saw the vision. Why didn't she ask to go back? Why didn't he encourage her to go back to the vision? She stayed in.

Knock is far from being above suspicion. Don't forget that the Church ignores the vast majority of apparition and miracle claims and understands how rife pious fraud actually is.  What is the likelihood that Knock is just another holy trick?