As a psychiatrist I diagnose mental illness. Also I help spot demonic possession (opens in new tab)

"Speaking languages they did not previously know – that is an extraordinary claim. All Gallagher has to offer as evidence is stories. Perception and memory are incredible flawed, especially so in a highly emotionally charged situation. How long had those attending the allegedly possessed kept their vigil before the interesting stuff started to happen? How sleep deprived were they? How willing to believe?

It’s also possible that a patient might memorize Latin phrases to throw out during one of their possessions. Were they having a conversation in Latin? Did they understand Latin spoken to them? Or did they just speak Latin?"

"... what if these are all just mentally ill patients with firm delusions, who happen to be smart and clever enough to do a decent cold reading? By accepting their delusion, you are reinforcing it, making it even harder to treat. You are victimizing the people you are supposed to be helping, by failing in your primary duty as a professional to be detached and evidence-based."

"But demons are crafty. Right, and aliens are super intelligent, and bigfoot can teleport, and psychic powers don’t work in front of skeptics. We have heard it all. These are all just lame excuses (post hoc rationalization) for lack of evidence."