All Introverted functions (Ti, Ni, Fi, Si) tend to derive their own understandings from within. Starting from early childhood, as they grow older, their personal understanding is built piece by piece, slowly and gradually. This personal understanding varies based on T/N/F/S—it diverges into things like Values, Logic, or Understandings and Structures. From there, they hold onto their internal standards and seek a place where they fit into the world.
▪️ As the name Introverted Functions implies, they involve a lot of inner reflection. Most of their time is spent inside their own mind or brain (the inner world).
Extroverted Functions (Te, Ne, Fe, Se) are the opposite. From a very young age, they adapt to understandings from the external world without first building their own personal understanding. It's only after relying on these external standards that they then reconcile them with their internal understanding.
▪️ If Introverted Functions (Ti, Ni, Fi, Si) work on developing their own understanding first and then try to fit into the world, Extroverted Functions (Te, Ne, Fe, Se) are the ones who try to fit into the world first, and then reflect back on their inner core.
This is a generalization. Their ways of operating are quite elegant on their own. While most people make decisions with their Dominant Function, it's important to note that everyone's functions alternate between Extrovert and Introvert.
This is what I mean when I say an INFJ goes Ni > Fe > Ti > Se (an I-E-I-E pattern), while an ENFJ goes Fe > Ni > Se > Ti (an E-I-E-I system).
Therefore, if a person's functions are in a balanced equilibrium, each in its proper place, we can say that person is fairly healthy. It's when any single function becomes overly sharpened and dominant that the balance is lost and things become unstable.