There is no specific purpose to this post. I'm mostly curious to see if people have anything interesting to say/add/refute. Apologies in advance for the boredom it may cause.
I am not going to challenge any of Jung's theory, especially since I haven't read any of his books. I highly respect the MBTI system, and think it's a fantastic tool for self-discovery. Hence, it has recently provoked some serious self-reflection on my part.
I don't know at what point I "became" an INTJ. Was it set in my DNA? Was it determined by age 5? Is it something recent? Most importantly, how can it change? Perhaps I'm not an INTJ at all, perhaps I've been moving away from it. How does one know what cognitive functions they use? How can they be scientifically measured? How much do they depend on the environment in which one is brought up? How much are they influenced by our brain chemistry, or genetic predispositions, or disorders? How much is set in stone, and how much can you change throughout your life?
Sure, people can be sorted into boxes, but the process isn't as straight forward as it's made out to be. I'm going to use myself in this example because I want to give a more concrete idea of what I'm saying. As a child, I was happy and energetic, but I also felt a strong sense of isolation from everyone around me. By age 11, I felt like no one understood me, and people were incompetent. This eventually led to clinical depression in high school. Can living in a particular state for years alter your personality? At this time, I would usually score INTP on tests. In grade 12, I smoked cannabis for the first time, and it led to an epiphany which forever changed my direction in life. I began a meditation practice, applied and got accepted into one of the most well respected universities in the country, and began to take control of my life and restore my health.
My life in university changed intensely and rapidly. I was in a demanding program, and for the first time in my education, I felt like I was challenged enough. I developed excellent time management and organizational skills. By second year, I became more social. I continued meditation and began to practice yoga regularly. I started attending parties, something which I despised in the past. I became associated with the raver community (most of which were also math/science nerds) and I could finally feel comfortable around people. I also began to take psychedelics, and had numerous mind-expanding experiences. I was once again the happy, enthusiastic, energetic, charismatic person I was as a young child. I became more open, more empathetic, more forgiving, more peaceful, more motivated.
Edit: The chemistry/math/computer science courses I took really changed my way of thinking as well. They probably boosted Ti use in daily life.
Two years later, I'm still growing in those positive directions. I feel like my personality did a complete flip from what it was in high school. Meditation reinforces my Ni, drugs make me aware of Ne, school has strongly solidified Te, and my large community of friends has brought out my Fi to the point that I question if it's exceeded Te. I score INTJ on 95% of tests that I take, but I think the bahaviour I've developed which I'm most comfortable with resembles an ENFP. I think to myself, "no, you can't be a feeler, you deal with the world rationally because that's the most fair way". This may be true, but my extremely positive and confident attitude seems to suggest otherwise.
Then there's the question of Ni vs Ne. Which one was natural, which one arose from years of meditation, yoga, and entheogen use? I can't see myself being a P at all. My everyday thoughts comprise too much of "this is what I need to do", "this is when I'll need to do it", "this is how the result will look like". If something gets in the way between me and my goals, I get very annoyed. Yet, my openness to ideas, my intense curiosity and agnosticism make me think otherwise. I'm not spontaneous, but I'm working to be more so.
I am not okay with being still. I love who I am and where I am, but I have a consistent need for growth, for discovery, for improvement. I don't know if that's driven by my genetics, my brain chemistry, or my life circumstances. I don't know if it can be attributed to specific cognitive functions or enneagram types, which are abstract theories. I don't know if I'm an INTJ, or an ENFP, or an ABCD. These are just useful labels, but they don't show the whole picture. People are consistently inconsistent, they are walking contradictions. Perhaps they can be fit in one of 16 types, but it's hardly trivial. Let's remember once in a while that we are humans who put ourselves in boxes we create; the boxes don't fit themselves to us to define us.
I leave you with one of my favourite quotes by Jung:
tl;dr: One's life history can make it very difficult to determine a specific type. Can certain experiences or conditions change our personality? I give a boring example of my own life =PI cannot employ the language of science to trace this process of growth in myself, for I cannot experience myself as a scientific problem.
~Carl Jung, Memories, Dreams, Reflections