The most recent examples were quite mundane, but what distinguished them from previous ones was that I seemed to be aware of experiencing two separate levels of consciousness simultaneously. I had just awoken and, still in bed, was listening to the radio. While following what was being said on the Today programme I sensed myself trying to open a locked window. I tried key after key and none would open the window, although at least one of them managed to turn the lock. So far, so banal, especially as the imagery was clearly connected with the fact that I’d just had new windows installed in my house. A few minutes later I was listening to a news item about the terrorist track on the train from Amsterdam to Paris, hearing and understanding each word. At the same time I was experiencing a dreamlike sequence in which I was involved in a similar but different attack. I glided away from the danger by slipping into a chasm which had suddenly appeared between two cliff-like walls. The Today presenter then moved on to an item about Jeremy Corbyn. As I listened I experienced myself undoing a piece of soap from a clingfilm wrapping.
Not much in the above for a psychologist to go on, I suppose. But bear with me. My most striking hypnopompic event happened a few years ago. In fact, I think it was my first experience of the phenomenon. Half awake I hallucinated – clear and vivid before my closed eyes and not in the blurry way that images are conjured up in the mind's eye – a black marble slab, like a gravestone, on which were engraved the words: “I breathed asbestos on the face of my poor father’s dead child.” I have no idea what it could signify. Even now it chills me when I think back to it.
Such hypnopompic and hypnagogic (referring to the same phenomenon just as you are falling asleep) experiences are quite distinct from dreams. While a remembered dream generally fades quickly and can be recalled only fuzzily and in snatches there is somehow a pressing reality about hypnopompic hallucinations which is hard to deny. So it is easy to understand how they could be interpreted as supernatural visions and spiritual encounters by those with corresponding beliefs. Even hallucinations such as my own – which range from the utterly banal to the incomprehensibly macabre – could be understood as conveying a heavenly message if I were that way inclined.
But the last word on the subject should go to Oliver Sacks.