Ghosts are either subtle bodied robots, holograms, or mind insertions. If ghosts are subtle bodied robots, either God has invented an alphabet of alternative matter which must be absolutely subtle as in, said robots must be able to pass through regular matter––or––in a less mind frying scenario––ghosts are particle based as in, ghosts are made of particles which can pass through regular matter. If ghosts are particle based, ghosts are composed chiefly of plasma or some alien particle that is unknown to man. The mystery particle is somehow contained by the form of the ghost which is achieved in some sort of matrix––perhaps not a skin since ghosts pass through regular matter––but more likely a forcefield. As to how the particle ghost traverses––it beats the hell out of me; I don’t know. Therefore, robot theory, rejected. If ghosts are holograms, a projector in some sense of the word is required. If ghosts are holograms, it does not explain how ghosts can touch people, therefore I reject this possibility. If ghosts are mind insertions, the human sensory can be exploited in full effect to emulate a complete experience with a ghost. A ghost which is telepathic, physically detectable by touch, and defiant of physics in apparition––that’s good enough. Therefore, ghosts are mind insertions––most probably.