I've been answering quite a few questions about Fi since I got on the forum, and they seem to be coming more frequently of late. I'm not quite up for starting a blog or anything, but I'm more than happy to have a small thread where people can ask their questions about Fi, or at least my interpretation of it.
On topic posts include any questions about Fi, or feel free to contribute your own personal description of what Fi is and how it works.
Here is a portion of a conversation about Fi that I was having with Whatever via VM, that the participants and a few witnesses agreed would be a good thread starter.
For me, Fi/Te makes perfect sense: the emotions inside of me are subjective and illogical, the world around me is objective and logical. It's actually kind of difficult to think of myself as being subjectively logical within myself, but objectively subjective with other people and the world around me.
I can "do Ti", but I don't have the "Ti values" of requiring logical self consistency. Rather I choose to adopt logical self-consistency for a short while, as needed. I can "do Fi", but it is more personal: rather than choosing to adopt a framework, I go inside myself and open a door. It's kind of like opening the door to a furnace, where one is almost afraid to touch it, for fear of burning oneself. All the other judging functions purposefully avoid this door: Te and Ti ignore it as much as possible. Te excels at ignoring others' "furnaces", while Ti excels at ignoring one's own. Fe mostly ignores one's own, while preoccupied with others: Fe deals with the pain of emotionality indirectly, from a distance.
Fi is the preference to face it all head on. Hence the vibe of "personal integrity." Developing Fi means looking at yourself, metaphorically naked, and understanding yourself, and forgiving yourself.
That last phrase is the most important part, especially if you have something really tough to deal with, inside. The way you open the furnace door and enter without burning yourself (or imploding or something ) is to arm yourself with forgiveness. You adopt a frame of mind and say, "It's OK. Whatever I find, it's OK."
Eventually, you will start deciding that certain aspects of your inner self are "not OK," but that's much more advanced work. If you decide that something isn't OK, and decide to try and "delete it," you might find out the hard way that you just deleted a core operating system file and crash. I believe the INFP tendency to be typically more emotionally unstable derives from this phenomenon: they decide to delete things while they're still too young to understand what they're doing, and they go crazy.
You know the Fi users that seem to have that wonderful aura around them? You know what I mean, it's hard to describe by being specific. They have an internal strength that is huge. They've faced their internal demons, saying, like Gandalf, "You shall not pass!" and won the fight, emerging far stronger than ever before. The demons aren't gone, of course, and may even be unleashed against those who deserve the wrath. Fi knows those personal, subjective demons, and they are under strict control.
Yet in spite of facing such horrors, they are kind and gentle, deliberately so, because of a degree of self-control that belies their seemingly random "P" type. When you violate one of their personal integrity axioms, you then face the indomitable strength of will that has defeated many personal demons.
That's the far end of the journey. Right now, your journey is more like that of a child, discovering wonders and horrors within yourself, and seeing them all anew as if for the first time. Like a child, keeping your mind open about how it all "works", not forcing any external labels or biases on your inner self (which is what Fe will try to do for you), just accepting it all as is. After a long while of cataloging, you eventually start learning what's what, and slowly begin learning how to face it.
Now here's the secret to Fi: be stubborn. Face yourself and do not back down. Don't hurt yourself, don't fight yourself, but just stand there (metaphorically, of course) and face all of that crap you don't want to see. All of the flaws in that wonderful gem that is you. What you'll start to see is that YOU are far more significant than all that random emotional crap inside of you. That YOU have the power to decide what you will and won't do. That YOU can take that which is beautiful in you and nourish it and make it grow to the point that it brightens everything and everyone around you. That YOU can stand up to all those fears and worries and hurts ... and instead of deleting them, give them so much love that they become lessons instead of wounds.