Jung’s approach is based on pairs of polarities. Getting eight functions with such a ‘binary approach’ requires three levels of dichotomy. Jung clearly explained his split of the rational functions into two opposite functions and the same for the irrational functions; but he never provided a theoretical context for a third “dimension” of psychological type.
Do you know people who tend to confuse left and right? –Not that they don’t know where their left and right is, but they mix up the words. Generally, if you ask them for directions you will notice that their hands point the correct way but their words don’t. The words right and left come out incorrectly, with no logic.