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In my opinion, reenforced by what I have read on the posts above, the existence of a spiritual dimension, or our belief in it, has as much legitimacy at least as the eleven dimensions necessary for string theory, which itself is a convenient way of explaining the numerous sub atomic particles.
So the theory of spirituality is therefore not as weird as some would have us believe.
Added to that is the evidence of personal experience, which is subjective and, agreed, not testable, but no less real for all that.