If you dig down deep enough, you get to a level that you can't understand rationally. I think that what passes for mysticism/spirituality is an attempt to put a rational take on those areas.

Some haunted houses use subsonic noise to generate apprehension in their clients...as a scientific fact, we know that level of noise causes anxiety, but we don't know why!

Maybe our rational powers will expand to understand those areas we cant understand now, but I am sure that when we do, we will run into a new level that we can't understand.