Interdimensional hypothesis (Ufology)

The interdimensional hypothesis (IDH or IH), or extradimensional hypothesis (EDH), is a position in ufology that proposes UFOs constitute contacts with beings from other dimensions coexisting separate from but alongside our own, as compared to the extraterrestrial hypothesis (ETH) that suggests they are physical beings from other worlds, travelling in "nuts and bolts" spacecraft. The earliest example of an interdimensional hypothesis was Meade Layne's Ether Ship theory of flying saucers; later, less spiritistic hypotheses have been advanced by such persons as John Keel, Jacques Vallée, and J. Allen Hynek.