I think the CIA figured out quite a while ago that psychedelics are a poor choice for brainwashing - they're too unpredictable in their effects and they tend to undermine the ontological bases of whatever belief system you're trying to inculcate in your subjects. If you're looking to set up a mind-control cult, it seems like depressants or dissociatives are better choices for spiking the kool-aid with. (Not that I spend a lot of time thinking about such things...

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Of course, the real problem with thaumaturgy as opposed to theurgy, whether drugs are involved or not, is that over time the practitioners can't help but start to believe in their own bullshit, and as the group gets more disconnected from consensual reality it all implodes in a dazzle of psychopathic power-games. As evidenced by the current behavior of the U.S. Republican Party.