There is no proof of the existence of 'spirits'. Yet belief in spirits is so common accross all societies, even isolated 'islander' cultures that have had little or no contact with other cultures for millenia, that I would call belief in spirits to be the 'standard' belief in the supernatural. Not belief in a 'god' or 'gods', there are many societies which lack this belief. But belief in spirits, particularly animal spirits and spirits of the departed, is the norm. Spirit possession is almost as common (the belief, not actual 'spirit possession' which is just nonsense).

There may be sound biological explanations for this. People have classified many of the 'altered consciousness' states that people experience, and there are two very common ones that typically get interpreted as contact with spirits. However, these can be stimulated with drugs, and have perfectly natural psychological explanations. There is no need to attribute a brief moment of 'contact' or experience of altered reality to the action of 'spirits'; not when non-supernatural explanations exist.

The clue for me is that while beliefs in these spirits are widespread, there was something like a 60/40 split in belief that the spirits were 'benevolent' or 'evil'. The interpretations of these 'contacts' was plainly influenced by culture, ie 'learned'. If these beliefs arose from actual contact with spirits, I would expect interpretations to be similar, at least recognizable descriptions of contact with some sort of entity. But no, interpretations are contradictory.

Jody image

  When words become unclear, I shall focus with photographs. When images become inadequate, I shall be content with silence.
-- Ansel Adams