Just to clarify what the occult researcher 'Colin Wilson' thought about a spirit world, after two decades research involving case studies, he did not dismiss the whole idea as some kind of collective delusion:
At this point in the development of civilization the aim is to re-establish that ancient contact with the 'unconscious', the realm of myth. This realm of myth is also the realm of man's 'hidden powers'. What the last two chapters should have made quite clear is that whether we like it or not it is also the realm of'spirits'. Ancient man believed in spirits not because he was a superstitious ignoramus, but because he often saw them. In that sense Voltaire and the French rationalists were completely wrong. Voltaire writes condescendingly in his article on superstition in the Philosophical Dictionary, 'All the Fathers of the Church without exception believed in magic. The Church always condemned magic, but it always believed in it; it didn't excommunicate sorcerers as madmen who were deceived, but as men who really had intercourse with devils.' And this, to Voltaire, was so preposterous that it was not even worth discussing. We can hardly blame Voltaire for taking what after all strikes us as a sensible attitude. The fact remains that we now possess factual evidence that enables us to go beyond Voltaire, and the evidence indicates that the world is a more strange and complex place than we assumed. Jung and Kardec seem to be in agreement on one fundamental point: that the road that will take us forward is also the road that will take us inward.
(Beyond The Occult - Page 286)