each spread is, therefore, a total picture, complete unto itself… The first six cards form a cross consisting of the four directions: North, South, East, and West… These six cards form the basic cross of the spread.
Greer argues that the Celtic Cross Spread constitutes a holistic, self-sufficient psycho-spatial structure mapping six cardinal directions onto the human body and psyche.
, Tarot for Your Self: A Workbook for the Inward Journey, 1984thesis