About a year ago I tried to understand the underlying principle behind all the functions. I got quite close but then things got muddy. I imagined a space with objects in it - a few of them alive, a few inanimate. All the objects have traits of all 4 extroverted functions and they are all linked with barely visible threads representing all 4 introverted functions.
When I started adding the functions, I realized I can add only S functions and there won't be any holes there. Everything will have their own traits and there will be a link between all the objects. It will be a very simple only physical world. To give it depth, you have to add N functions. Aside from Se traits the objects now also have potential and non-physical connections.
Then I added T and F. It doesn't matter which one is added first, both give a fully adequate addition to everything. They don't depend on each other. However, both T and F depend on the other traits of objects - objects must have both S and N traits already before they can be seen as useful (Te) or good (Fe).
Makes sense to me. The most important part is Se and Si because they give everything dimensions and form. Ne and Ni just add to the world, they aren't as required as Se and Si. However, T functions and F functions are equal fut give opposite kinds of impressions about the objects.
But this is how far I got.
I was unable to figure out why the functions are always paired. Why does my Fe need Ni by its side and if it really needs some S/N function, then why can't it be Ne or Se. Why do I benefit from other people having Ti? What does Ti give that no other function could. But still... if I can imagine this space with T and without F, then why is there sudden synergy between T and F types? And if I can imagine this space without any T or F then why do all people need either T or F.