There are hallucinations: "perceptions of objects with no reality," there are visions: "a supernatural appearance that conveys a revelation," there are dreams: "a series of thoughts, images, emotions occurring during sleep."
There are strange, uncommon things in our lives. Mysteries. How to explain them? A Person Known To Be Dead, coming for a chat? Where does that fit into your cosmos? How to get your head around that?
A visit from the dead? A visit seemingly as real as you or me? As "real" as anything else you can conjure or imagine, or perceive? "Not artificial, fraudulent, or illusory."
Some things you can't explain. You just experience them. And remember. And in that way you and your world become a bit deeper, stranger, weirder, more mysterious.
You think you are more than your body. Reality is more than you know. There are platforms, tunnels, doorways, windows into other worlds within and around us.