While psychologists may be able to identify specific clinical pathologies in the thought patterns and behavior of the conspiracy-minded, for me the hallmark of the conspiracist personality is its naive religiosity, which is surprisingly akin to the all-encompassing, steadfast piety of very young children. Children and conspiracy theorists are philosophical occasionalists, in that they believe that everything that ever happens is an occasion for a transcendent power (God, proponents of One-World government) to impose its will. They are magical thinkers (if I step on this crack, I'll break my mother's back) and obsessive pattern seekers (if a Rothschild handled Cecil Rhodes's money, then Rhodes scholars must all be Zionists). They accept that appearances can be deceiving (a frog may turn out to be a prince; Hillary Clinton is really a Jewish lesbian named Rodenhurst) and never doubt for a moment that someone, somewhere, can provide the answer to any question, not matter how vexing (a parent, a pastor, a third-party political candidate). Not that there aren't significant differences between children and conspiracists. Children forgive and forget; conspiracists store up their grudges and grievances and keep them fresh for centuries.
Quoting the Roman poet Archilocus's aphorism that "the fox knows many things, but the hedgehog knows one big thing," the philosopher Isaiah Berlin famously contrasted the intellectual styles of pluralists and monists. If conspiracists were intellectuals, they would be hedgehogs, but they're not usually thinkers - they're people of faith, more often than not, and usually of a fundamentalist bent. The object of their faith is not necessarily religious (though it frequently is) - I am referring to the manner of their believing rather than its contents. Uncritical and credulous in regard to their own authoritative texts, dogmatic and literal-minded in the ways they interpret them, conspiracists attribute those same qualities to their adversaries. Not only do they grant credence to outrageous libels - for example that the Talmud instructs Jews to defraud gentiles, or that Jesuits pledge to murder as many Protestants as they possibly can; they take it for granted that all Jews and Jesuits would honor such unholy covenants. Instead of dismissing the blasphemous writings of occultists out of hand, the conspiracist fears them; stranger still, he believes them. Because the conspiracist is God-fearing, he sees the hoofprints of Satan everywhere.
...As illustrated by innumerable Zen parables, the ability not just to tolerate but to revel in mystery and ambiguity is a signature of enlightenment - an attribute no conspiracist, for all the priveleged knowledge he or she claims to possess, can lay claim to.
"The only true wisdom is knowing that you know nothing," said Socrates. Conspiracism is the delusion that one knows everything.
Splat goes the theory
4 hours ago