If you can't define it, can't explain it, can't detect it with any known scientific instrument it doesn't by definition exist. We may as well be talking about being tickled by invisible pixies. Spirituality only has a psychological explanation that the person feels an overwhelming satisfaction and contentment from any number of any number of real and individual reasons. Personally I can get that from having a good dump on the toilet, watching a movie, having beer with friends, being in love or repairing a door.