All of these holidays are rooted in ancient mysticism. They all celebrate the ending of the warm summer months or the light part of the year and the begining of the cold and dark part of the year. The symbolic death and eventually rebirth of our yearly solar cycle is an apparent metaphor for our own human life cycles, birth, maturity, decline and death.
Our ancestors believed that the veil between the living and the dead  was at it's thinest point on this day and that actuall communication with the deceased was possible.
I have taken part in neo-pagan samhain rituals and have felt the "spirit" of the season first hand. there is def something to this holiday as a symbol and perhaps something more spiritual and unexplainable at it's roots.
One thing is for sure, many different cultures and peoples from all over the world, (europe, americas, africa) have all held festivals and festivities celebrating this season which seems to be as old as the dirt.
happy halloween
ar2