Socionics is a model. It seeks to describe human relationships.

The simplest way to have a network of interacting nodes is to have each node have an "in", and an "out". (This is your ego block; the other 3 blocks are just ways of describing specific phenomena related to your specific "in" and "out"--they are logically superfluous and exist solely for clarity's sake.)

As for why there are 8 functions and not some other number, that is a Socionics history lesson I cannot administer.

etc etc can someone please finish this thought for me?

EDIT

Quote Originally Posted by Skeptic View Post
And beliefs (that exist independent of the knowledge described above) are harmful. Their existence within yourself is a crime to yourself and to humanity as many of them are seemingly harmless but blind us to the reality of the situation, causing us to make unethical decisions that are not supported by reality.
That is a result of their abuse, not their use. The minute you use Socionics as a script is the minute you cross into abuse. I have not had this problem of abuse except in one situation. In all other respects Socionics has been a boon and helped me to understand and let other people do as they please, and there have been many similar reports both on the forums and from people I have introduced the theory to in the real world.