Here's my own thinking on the subject. Everything's relative, so Fi has to be examined in the context of Ti, and even in the context of Te and Fe.
Everyone's usually pretty clear on what Te and Fe are. In my own shorthand, Te is short-term analysis and rationalizing for organizational purposes. Fe is short-term emotional bonding and relationship-building for organizational purposes. (I know those definitions will be challenged, but I'll go with them for now and you can judge for yourself subsequently whether those definitions are critically flawed for purposes of this exposition.)
Ti and Fi, then, are the same things as above, but introspected into the form of a system: Ti types analyze and rationalize in order to build logical systems. Fi types study emotions and relationships in order to build value systems.
What's the difference between the extraverted and introverted versions of T and F? Fe and Te place a high value on the social contract as a means of dealing with life. I'll hypothesize that Te and Fe types were valued as caretakers and contributors when they were children; they were rewarded for participating in the community (the family) and taught not to value solitary accomplishments. By comparison, Ti and Fi types place a high value on the solipsist self as the best tool for dealing with life. Frankly, all the Ps (Dominant and Auxiliary Ti and Fi types) are kind of whiny and selfish by comparison to the average J.
What's the difference between Fi and Ti under this scheme? Again, I'll hypothesize some formative childhood influences, just to create a paradigm--a fun little tool for understanding the differences in type. Ti types often seem to have been raised in chaotic environments in some key ways--a demanding parent, a suffocating parent, squeezed by strong or simply too many siblings, etc. Unable to compete on an emotional (bonding) level, they strive to win their fair share of the family pie by relying on rules and logic. Thus, let's say that T is motivated by a need for fairness in order to deal with emotional chaos. Fi types, on the other hand, seem to carry old wounds from abandonment or lack of attention. Let's say Fi is about building emotional bonds in order to address fears of abandonment or lack of attention.
Is Ti more grounded in reality than Fi? Not at all. Both types get their original inputs from the world around them. In the process of introspecting systems from those inputs, both types may remain connected with the outer world or may become increasingly cut off from the outer world. If both are connected with the outer world, they can probably offer sound reasons for the introspected systems that they create. If both are cut off from the outer world, they may have trouble justifying their systems, rationales, and behaviors in the real world. Fi types may become new agers, believing in things because they "feel right"; Ti types may spend their lives studying and becoming proficient in Klingon or archiving libraries of old train schedules, apparently for no better reason than because it gives them a bit of notoriety in a tiny subset of cultish types who share that interest sprinkled around the nation, even as they become totally estranged from the family members who live in the same house with them.
Even when they can offer reasons for their systems, are the base beliefs of a Ti any more reasonable than those of an Fi? Many's the time I've asked a Ti why he treats a spouse or a family member in some strange fashion. "Because it's fair." But is fair really the issue here?--that person should hold an honored place in your life, and you're treating them like the family dog. "I treat people fairly. I can't explain it any clearer than that. It's just who I am. If I gave my wife or my kid better treatment than the family dog, I wouldn't be me anymore."
Frankly, it's the same ridiculous answer an Fi might give when pushed on why he won't accept the precepts of basic math or science. The Ti person is no more in touch with real life than the Fi person. They're just two sides of the same coin. The Ti person can't simply choose to ignore the rules of emotions and human interactions any more than the Fi person can simply choose to ignore the rules of logic and science. To do so is to prove how badly one is out of touch with reality. IOW, the Ti function offers no more protection against falling completely out of touch with reality than the Fi function.
Both types will survive and even prosper, but if they persist in their one-sided development their lives and their introspected systems will be severely and obviously (to an outside observer) deficient in key respects.
So what's Fi? Pretty much the same thing as Ti. Emotional systems and hierarchies will be mulled and constructed pretty much the same as logical systems and hierarchies. Raw material will be taken from the world. If the Fi or Ti person believes strongly in God, then God is going to appear in both systems. If the Fi and Ti persons are both well-educated and in good contact with the world, then they'll both be able to argue their systems coherently and exhaustively; for example, if the subject is the death penalty, then perhaps the Ti person will tend to pull out a lot of law books and the Fi person will tend to pull out a lot of philosophy books on the subject of the value of life. Neither argument will automatically or intrinsically be stronger than the other. Law and philosophy ultimately draw their water from the same well--real life.
And if the Fi and Ti persons are grossly solipsist and out of touch with the real world, then the Fi person is going to belong to some new age cult or live in a world of bunny-rabbit and butterfly and rainbow stickers on their windows and wonder why they never seem to find true love; the Ti person is going to belong to some Heavens Gate cult or live in a one-room studio with bare walls and spend their lives prowling the internet pushing some conspiracy theory and wonder why they never seem to find true love.
Big difference. :rolli:
