The family of one of my patients has a website up on his behalf, to free him from the horrible injustices the various governments local, state, and national have visited on him by locking him in a psych hospital just because he threatened to kill people and thinks that Special Forces in Iraq put a chip in his head. We discussed the site at team today.
Our PhD psychology student surprised me by asking about conspiracy theories. After my very general answer, he started talking about the website Loose Change and the Twin Towers. By jiminy, he's a Truther! He started in about kerosene mix and jet fuel but I cut him off. "Popular Mechanics has it covered. Straightforward. Thorough. Check it out." He seemed disappointed and wanting to discuss it further. I was brief, and I am sure he thought, dismissive, but I didn't say "It's just nuts," which is what I was thinking. I noted that the evidence offered by the conspiracy theorists was unconvincing - they lean toward an explanation of single events that is barely possible. Additional barely possible explanations do not strike them as reducing the chances that their theory is correct, but confirming it. Aha! Mayor Willie Brown was warned to be cautious about flying at his Sept 10 morning briefing! You see?
But Willie Brown got those warnings about once a month. The mayor of LA didn't get a warning; the mayor of San Diego didn't get a warning; the mayors of Oakland, Sacramento, and Son Jose didn't get warnings. Mayor Brown reported his info immediately in case there was some lead there. And we never heard any more about it! That just goes to show it's possible there is a coverup...
The student shook his head worriedly and said that the scary thing is that it's even possible. Ah yes.
Simple declarative: belief in the probability that some sort of conspiracy is happening precedes all data. I have had folks protest no-no-no! I never suspected Bush in the 1990's, I hadn't even heard of him! I only gradually came to think he and Cheney might be involved. Nonsense. You've believed in some sort of conspiracy for decades, and gradually came to think that Bush might be part of it. The details have been vague and somewhat flexible, but the repeated themes of corporations...conservatives...military...intelligence agencies have been constant.
The belief precedes the evidence.
Update: the team psychiatrist, referencing conspiracy theorists, noted another explanatory bit: they regard secret information (often unsubstantiated) as more important than obvious info. The Physician's Assistant had a good example: conspiracy theorists will believe a convoluted tale about the acquisition of hammers - which can be weapons, y'know - and not ask themselves "why would they go through this when you can go down to the hardware store and buy a couple?"
It is interesting to contemplate what their life experiences have been, and how their minds work, to believe that the doubtful hidden must be more important than open knowledge.