Nitpick: There is only lack of evidence for a force which only interacts between brains There is already precedent for an event on one scale to change the total force exerted on that scale: the mass change of atomic reactions, resulting in a change in the amount of gravity exerted by a closed system with no energy transfer.
If there is also a force exerted by brains or on brains that is different from that exerted on the same number of brain cells that are not brains, analogous to the force exerted by atoms which is different from the force exerted by the same number of protons, neutrons, and electrons that are not atoms, then physic phenomena.
I don't think that psychic phenomena have been demonstrated to be more likely than hallucinations, but I don't think they would be as strong evidence against reductionism as is suggested- but they would be very strong evidence that our current reductionist models are incomplete.
Today's post, Psychic Powers was originally published on 12 September 2008. A summary (taken from the LW wiki):
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