It is a matter of both cultural perspective and available education. If you have a deeply spiritual society, with an education system that supports spiritual approach to the way the world works, you will get shamans or spirit mediums or spirit priests or spirit doctors.
As for barbarians...
The short version: shamans are not barbarian analog. Spirituality does not equate low level of technology. Barbarian does not mean not civilized.
As for barbarians...
Where did the word “barbarian” come from?
The word “barbarian” originated in ancient Greece, and was initially used to describe all non-Greek-speaking peoples, including Persians, Egyptians, Medes and
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The short version: shamans are not barbarian analog. Spirituality does not equate low level of technology. Barbarian does not mean not civilized.