I think that a belief in human spirituality is simply a means of sublimating and rendering intellectually acceptable a pre-existing gut-level belief in a higher supernatural power. It's just a smokescreen thrown up by people who desperately want to believe in something, but won't let themselves believe in a 'God'. If you believe there are such things as 'matters spiritual', you are de facto admitting you believe in the human soul - a wholly religious construct.