In the jungle the old felas say "every thing has an oppisite , just like two sides of a coin. If there is a physical world then there is also a spiritual world"..
Also how you interpret ghosts depends on your beleifs ... the same experience attributed to: ghosts , demons, spirits , aliens , 3 week old burrito , drugs side effect , richard GAY simmons blowing you kisses ...
There is another world out there ... come with me and I'll show you IN MY PANTS !