Historian Richard Hofstadter used the phrase “paranoid style” to describe conspiracy theory thinking that was like paranoia, but not clinically diagnosed as such.
My mother suffered from dementia in the last year of her life. She believed that my father and close members of her family had spirited her away from her home and that she was currently living under the bed in a hotel in a nearby city. I know from personal inspection that this was not true. She was still at home, not in a hotel and not under the bed. Nevertheless, nothing I, nor anyone else could say changed her mind.
On one visit I would show her a piece of furniture she had had for 50 years and say, “isn’t that yours?” She would reply, “it looks like mine,” but a string of such confrontations made no difference. I tried reasoning; she said, “you would have made a good lawyer” and in the end she said “are you part of this?” By that, she meant to ask if I was part of the conspiracy. It was a sad experience, particularly in the breakdown of the relationship between my mother and father, since she became afraid of him, as the alleged leader of the conspiracy that was keeping her in the hotel.
From this experience, I’ve learned the power of delusion and it is perhaps the reason that I find it easier to sympathize and to forgive the birthers.