Jung distinguished four main foci of reality perception: Thinking,
Feeling, Sensation, and Intuition, which, in combination with extraversion
and introversion, provide eight main psychological types (Jung also
outlined some of the 16 types via the Auxiliary function, e.g. “practical
intellect for instance paired with sensation,” which we call “LSE” and
“speculative intellect breaking through with intuition” which we call
“LII”). This model was first offered by Jung in his work on the psychology
of individuation: Psychological Types. His theoretical constructs were
coined in parallel with their practical verification. Second only in
importance to extraversion/introversion (vertness), Jung emphasised
another scale marker: rationality/ irrationality (this was later expanded
upon in Humanitarian Socionics in its formulation of the socionic
temperaments). So, the system of differentiation characteristics is a set of
four dichotomous scales (that divide into two poles): logical/ethical,
sensory/intuitive, extraverted/ introverted and rational/irrational.
Combining these characteristics creates the following types.