It's not my favorite word and, imo, got thrown around here needlessly a while back. But this can be how it feels to have someone messing around with "facts" or things that the person "knows"...while not necessarily being what you're doing.
http://www.urbandictionary.com/defin...rm=gaslighting
http://en.wikipedia.org/wiki/Gaslighting
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But it's more than just "facts". For Fi, the internal structures are very personal, and built off personal and emotional links of attraction/repulsion. This does make their internal structure very personal, and chemical/hormonal. As in if you try messing with the Fi internal structure, you are messing with brain parts (ie hypothalmus, amygdala, etc) and brain chemicals. This gives it a very personal feel to the process.
But please don't mistake Fi structures as being the same as Ti structures. Ti structures are based off abstract rules, abstract links, categories, etc. You can easily recategorize things or alter some rules and reality doesn't change. Just the view of reality. And that's fine, imo. "The map is not the territory." And what you're messing with is the map. (Admittedly, many people with strong Fi forget that their emotional structures are merely personal maps as well, not the actual territory.)
But, when you start messing with the territory, that is a whole different matter.
Like, for me, for example, I rely heavily on my emotional links as memory triggers, and things that were said, done, or events that happened. The parts that don't need interrpretation. As in he said this, she yelled then left immediately afterwards, an hour later he walked out and discovered his car had been keyed. (Made up scenario.) Those are "facts" that I can count on, explicit things that happened. Which can be interrpreted in a number of ways. Now, if a person draws the conclusion that she keyed his car, and you were to try to get them to see other interpretations, that's fine...unless you started messing with those facts, such as rearranging the time frame, saying that something else happened when you either don't know if it did (a "what if" but stated as truth) or if you were to flat out give false information. This is akin to messing with the territory.
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Another possible example:
Have you heard of chaos magic? Imo, it's very Alpha NT. My understanding of it is that these practitioners will deliberately create, rearrange, or destroy their personal abstract structures, the rules they grew up learning, their own understandings of the world, and recreate or rearrange a new structure. This process might be akin to using drugs as a way of gaining insight or new experiences. A way of breaking free from old chains and expanding one's mind regarding one's world.
Unfortunately, if they aren't careful, they might have a psychic breakdown. Delusions are a common side effect. And imo, it was pretty freaky to read the writings of "heavy" practitioners. (But then, I also had to question how much of what they wrote was real...and how much was made up in the telling...a way of keeping the myths of chaos magic alive, or of fitting in...or other???)
I think most of these people I had read or looked into were NeTi. And I think that while they may have played with destroying and creating abstract structures (abstract maps) I also think that their Te Demonstrative (the subconscious awareness/acknowledgment of the territory) may have helped keep most of them from total break down.
(Note: i edited and rearranged and deleted chunks, hopefully the above is understandable at least,
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Back to gaslighting. So basically, gaslighting can be messing with the map, and it can be messing with the territory. And for those who have very personal maps, they might not be able to tell the difference. And messing with the map can feel like messing with the territory. Which is where the Te comes in...Helping them see the separation between the territory "facts" vs their personal map.