I’ve been using the MBTI functions as a way of sharpening focus on the four temperaments.
This is because pragmatically the functions allow a finer-grained analysis of the temperaments.
For example, what’s the difference between a melancholic-phlegmatic and a melancholic-sanguine?
Both are NF types. Melancholic-phlegmatics are xNFP and melancholic-sanguines are xNFJ.
This means that melancholic-phlegmatics are using extroverted intuition (Ne) and introverted feeling (Fi), whereas melancholic-sanguines are using introverted intuition (Ni) and extroverted feeling (Fe).
So in the first instance, although both are melancholic with the combination of feeling and intuition, the NeFi combo is already a more introverted way of being than the NiFe combo. Fe is externally oriented, meaning that the melancholic-sanguine makes decisions according to their sense of how others are feeling, for the sake of group harmony.
Fe types want to connect with others and maintain good relationships, whereas Fi types are more motivated by internal coherence and authenticity.
In addition to the orientation of the feeling function, the third and fourth functions of either type also play a role in describing the difference in temperament.
Melancholic-phlegmatics’ third and fourth functions are extroverted thinking (Te) and introverted sensing (Si). Melancholic-sanguines’ are introverted thinking (Ti) and extroverted sensing (Se).
The significant part here is that Si and Se are the determining functions of the phlegmatic and sanguine temperaments respectively. Si gives the phlegmatic their inward, mnemonic focus. Se gives sanguines their sensory, outward, experiential focus.
That’s why these two types of melancholic can be similar, yet in other ways so distinct. What makes one melancholic partly phlegmatic is the inward orientation of their Feeling function plus their introverted sensing (Si) in third or fourth place. What makes the other melancholic more sanguine is the extroversion of their Feeling, plus the extroverted sensing (Se) in their third or fourth place.
Or is it…
But the functions are just useful, finer-grained descriptions. No one knows if they are actually different cognitive functions, and so we can ask which is the underlying reality: MBTI functions, or temperamental factors?
What I mean by temperamental factors is that the four temperaments are typically described as combinations of two factors – the clearest of which (in my opinion) are excitability and duration of impression.
Given that a melancholic has low excitability with enduring impressions, but that melancholics differ by degrees, we can ask the following interesting (but not very pragmatic) question:
Are the differing degrees of melancholic due to real differences in cognitive function, or are supposed differences in cognitive function just ways of describing varying degrees of melancholy?
In other words, are Fi and Fe different things, or are they just different degrees of the same thing?
As far as I can tell, it’s quite possible that Fi is really just a less excitable form of Feeling, and Fe a more excitable one.
But going a step further, I’m not sure that Feeling and Thinking are necessarily different things either.
It’s plausible that F and T represent less excitable and more excitable forms of the same cognitive process. In effect, F is like a blurred and impressionistic version of the sharper, detail-oriented T.