I've been trying to figure out the correct derivation for some time.

We have:

Attitudes: I/E
Functions: N/S, T/F
Rationality: J/P

How did the final element structure evolve? I have some thoughts depicted in microsoft paint:

Idea 1




Idea 2




I prefer the former, partially because it might include the latter as a sub-system.

Alot of this topic may be muddled with conceptual distinctions that are irrelevant.