There are some things I want to clear up because I found what you said earlier interesting. I'll go through your first post and cherry pick some things here and there that I resonated with and others I didn't.
Fi is the way I structure my thoughts, emotions, experiences, observations, etc. Think of a cave mouth. You enter it and underneath is a vast space filled with winding catacombs, stalagmites and stalactites, pools, and rivers. Multiple tunnels branch out and in. It's confusing to an outsider but the whole thing is meticulously organized. New perceptions are placed inside, adding to the labyrinth. Stalactites are refined by running water. Catacombs are smoothed with footprints from much exploration. It's a system of careful organization and it's very, very large. Sometimes even I get lost there.
I think this is a good example to describe the complex nature of Fi. But honestly, the way you describe this sounds very Ne to me. Maybe it's because I don't incorporate a lot of colorful words and metaphors into my writing, but just the way this whole paragraph is structured gives off a more intuitive vibe overall.
Se is commonly perceived as a thought process and it's not. It's a way to information gather. Fi information gathers internally. Se information gathers externally. That is to say that Fi utilizes a great amount of thought about meanings and abstractions, or in other words, things that can't be touched, seen, heard, or smelled, but can be felt emotionally. There is a system of careful analysis which is helped by Ni in the ISFP. Deciphering patterns, making connections, testing them, and refining connections. Testing is where Se comes into play.
The part in bold sounds very Ne to me too, but I think I understand what you are saying. You are talking about hands-on experience rather than abstract concepts, right? ISFPs are able to make, test, and refine connections as long as we have experienced it firsthand, rather than simply theorizing about something?
I need to reality test to figure out whether my Fi is giving me an accurate picture of the world. To figure out whether I'm organizing right. There has to be some external connection or information gathering process or I'll fall into a world made up entirely of my own mind. I've been lost there before and it really can destroy you in a lot of ways. Relying on the Fi-Ni loop means that you stop taking in new information, which is something your world view can't grow or adapt without. Se is in service to Fi because Se, or experiences, give your Fi a more accurate picture of the world, of others, of yourself, and help you to develop as a person.
Se makes an ISFP adaptable and open to new perceptions. The Fi-Se-Ni combo makes ISFPS masters at juggling and integrating perceptions, at viewing multiple things from multiple points of view. At understanding others, understanding why they think the way they think, and taking that into consideration, both to accomodate others and to expand their own views. ISFPs are keenly aware of who they are and who they could be, and the possibilities inherent in that.
I like how you describe this, but isn't tert-Ni more of an "aha" moment that comes out of the blue because it's not one of the two main functions we are totally comfortable using? So in other words, it may not necessarily show up when we need it? But I have read that ISFPs can develop their Ni function over time to where it can work in close proximity to Se, is that what you are referring to? I'm not too keen on the tert-Ni function, so maybe you can elaborate on where I am missing the point or not. In addition, I'm still unsure if I need external connection/information to come to depths with understanding the world around me. But maybe there were times I was in an Fi-Ni loop without realizing it and being too comfortable in my own mind.
It's less about eating an apple to figure out what it tastes like and more about eating an apple because an apple is part of the universe, and eating it will tell me about the universe in a spiritual way.
I don't relate to this at all. If I decide to eat an apple, I would eat it solely because I am hungry and it's a healthy snack that tastes good. There is no spiritual context I am thinking about during that moment whatsoever.
I think there is a misunderstanding going on and I realize I'm not always good at articulating, and can struggle to describe things with clarity.
This is probably not made as an example towards ISFPs, but I want to say that I also struggle with articulating myself in words. I can picture the idea in my head, but once I am made to project my thoughts into words, it becomes very difficult to do so in a concise manner. Everything comes out jumbled up. I think this could be a common ISFP trait, since we tend to be more visual I would assume.
I realize now that saying "land of ideas" makes it sound like I live inside my head, which isn't what I meant. I meant more in a land of possibilities, which is what happens when you're in the moment. Like being aware of all possible actions you could take and just sort of understanding them all at once and making a decision without a long analytical process. A gut thing. So it's not going from one possibility to another and another, it's sort of seeing all posibilities and zeroing in.
I relate to this, but I also have an e6 possibly second in my tritype and you have it first. Could you maybe be confusing this with the cautious side to an e6? Just a thought. Although, this also sounds very Ne to me too, the whole thinking about the possibilities of a situation. In reference to ideas, sometimes I get an overwhelming bundle of ideas that flow in my head, but other times I can't come up with anything, like an artist's block. But this pertains to anything in general and not just artistic outlets.
On a side note, there are other things I could relate with INFPs, the whole daydreaming, idealistic, future/past thinking, and multiple perspective part mainly. Could it be possible for ISFPs to be idealistic? I've always considered myself that, but maybe it's just me being overly picky. I relate to getting lost in daydreams and forming my own stories in my head with other possible ideas I can add to make them fit this fantasy I dream of. Do you also fantasize about the past? Sometimes I look back on past events and think about alternative ways in how they could have formed to my own liking. The same happens for future events too, like envisioning what could happen at an event and then becoming disappointed when it doesn't turn out how I idealized it.
And the practical aspect of ISFPs I don't relate to at all. I am one of the least practical people ever. I don't do things just because they have a practical means to them, but rather if I am intrigued with them just for the sake of it. I do, however, consider myself very detail-oriented and can see many things that others wouldn't notice. But there are other times I have to try really hard, like when I am scrubbing the dishes and end up leaving some food stuck there without noticing it until someone else points it out (even from growing up with a crazy, OCD-like mother, I still can't clean things right)

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However, the main reason I decided to identify as an ISFP is because of a gut feeling I had inside and because it always took much more effort to decipher abstract concepts. As a child, I was naturally much better at hands-on activities than absorbing concepts from textbooks. Moreover, I am a walking stereotype of one, being an artist an all. I've always preferred drawing and painting over writing, which is known to be more of an INFP thing. But I must say, something that occurred to me recently is that I'm not very good at taking the main idea of something and breaking it down into smaller increments of it. It's much more natural for me to start small, like with a seed that grows into a tree with many different branches and leaves, if that makes sense. I think the latter is more in line with ISFPs.
Sorry, I'm sort of spinning this towards my direction and going off tangent, but I just want to find some common ground to see if you can somehow relate, since you seem pretty knowledgeable in understanding the ISFP psyche. Although, others are suggesting that you are probably an INFP, and I'm getting that vibe from you too. But I understand there are inaccurate stereotypes that you are trying to disprove as well.