Why is socionics the way it is?
I've been studying socionics extensively now, turning it every which way, and still can't figure out why its basic assumptions are what they are. Any sources I find only describe what the system is, not why it is. If the main principles were empirically obvious in practice, the lack of justification could be excused, but they clearly aren't - typing is notoriously difficult, and predictions are even tougher. I hesitate to use a system if I cannot see the full reason behind it, because I thoroughly suspect that one's ideas heavily influence one's perceptions, and virtually any proposition can be "proved" if you try hard enough. I don't suggest that socionics has no basis, but have had a terribly difficult time trying to decipher it.
Mainly, what I want to know is:
How are the particular properties of the functions and elements explained and justified from the ground up?