Ross Douthat has a long-but-interesting post about the “paranoid style” (or mostly about that as it applies to George Lakoff of Berkeley). I don’t disagree with anything he says, but I would put my own view on the subject a bit differently: Paranoid people tend to assume other people have their own motives. Obviously this can get more complicated, but at a basic psychological level conspiracy theorists, for example, tend to assume there are conspiracies everywhere precisely because if they were in power they would be hatching conspiracies themselves. It never surprised me that Sidney Blumenthal was concocting crazy, often absurd, theories about other peoples’ schemes because he is by all accounts precisely the sort of person who — given the slightest opportunity — hatches similar schemes himself. Similarly, when men are put in confined areas with limited food or water, they almost instinctively form coalitions and schemes to prevented others from doing the same thing to get the resources first because they assume that’s precisely what the other guys are doing.
I agree with Ross that conspiricism is a desire to make conflicting facts and events rational and coherent. But the one thing the paranoid conspiricist always assumes is that discordent facts are connected by a deliberate will on the other side. “You think it’s a coincidence the Ohio recount came out the same week as the tsunami!?” Once you accept that everything bad that happens to you is the result of someone else willing it to be so, it’s an easy leap to assume that person is not only your enemy but that he’s got incredible forces at his disposal to make bad things happen to you.