One wonders by what devious arts a bedridden mystic, barely able to move, would be able to fool educated observers sitting round-the-clock at their bedside.
One might wonder that, but there is a large literature on creating illusion. Most methods take advantage of observers' cognitive biases and unwarranted assumptions. For instance, if you were thinking that the bedridden mystic would have had to get out of the bed and stealthily go fetch food and water himself, in order to practice such a deception, you've already half fooled yourself before any of their "devious arts" even come into play.
As a devout Catholic they would also be aware of the meaning and consequences of sin.
And? I know many devout Catholics. They are indeed aware of sin, they have an entire practical economy of it, accounted for to the last penitent Our Father. Accordingly, they sin all the time, just like everyone else.
A competent doctor would not[e] his observations and base his conclusions on that, not any materialistic beliefs he held.
If a doctor told me that I had all the observable symptoms of influenza, but since he had not personally observed me inhaling any influenza virus particles he's concluded that a supernatural force must be afflicting me with a curse that exactly mimics the effects of influenza instead, I would call that doctor incompetent.
In the case you describe, the doctors observed all the signs of a person adequately nourished and hydrated, but because they did not personally observe the person taking in food and water, concluded that a supernatural force must be miraculously (either) providing the sustenance or preventing the expected effects of their lack. That is no less incompetent.
The doctor and the priests have no purpose being present, at the bedside or in the story, except to set up for confirmation bias and add to the cognitive illusion that some sort of difficult decisive expert verification took place. What is a doctor's expertise going to be able to add to the understanding of what was going on? That the mystic didn't have a disease? (No one was saying he did.) That the mystic had not perished from hunger or thirst? (That's pretty obvious and doesn't require a doctor.) That the mystic wasn't obtaining food and water by deceptive means? Doctors have no training in determining that! Nor do priests.
From the many accounts I've read the inedia and stigmata were gifts conferred upon them, not decisions they made.
Then since the Bible clearly instructs us to pray "Give us this day our daily bread," can we safely conclude that the "gift" of inedia, if the mystic actually had it, must have been conferred by demons?
I think they sat at the bedsides of some mystics for weeks. Some of these mystics went without food and water for decades.
Here you fall for another common cognitive illusion (or else, you expect me to fall for it) that weak evidence weakly supporting one claim somehow strongly confirms a more extreme claim. How does some doctors and priests observing mystics for weeks in any way confirm the claim that they went without food or water for decades? It does not, of course, though it might seem to if you don't think about it. Even a whole audience of doctors and priests fails to understand how a magician levitates four feet, suggesting that just maybe the magician really does have miraculous powers, should we believe the magician's (or his publicist's) claim that he can levitate to the moon?
