Two or three times in my life I have felt something like what James describes, the feeling of something being really present in the room that had no physical form. If I had to describe its "appearance" I'd say it was like some kind of pulsing blue crystal several feet tall, floating in the corner of the room. At the time I felt an abstract sense that this thing was very significant and powerful, although it didn't speak to me or move me to do anything in particular. All of these experiences happened late at night as I was drifting off to sleep. Each time when I woke up in the morning the vision had lost all of its significance. But perhaps if I had been experiencing the kind of spiritual crisis that James will describe in the lectures on conversion, I might have made more of it.