One of the most difficult aspects of understanding spiritual experience in any general way is the absolute privacy of the experience.

I might liken them to dreams - as vivid and peopled and complex as they may be, no one else is ever actually having them with you. Even an experience "shared" by two people side by side at the same time is not perceived the same way - and I mean this in a much more meaningful way than that of the slight differences of observations of local sensory stimuli. I mean that while there might be great similarity at times, it can also be that the "shared" experience is wildly divergent, or to use a clearer example, present in one person and not at all in the other.