Are you an INJ? Did you have trouble initially deciding whether you're an NT or an NF, despite the fact that the two are completely different temperaments?
If you're an INJ who totally resonates with their temperament, or someone who believes that individual letter preference strength is independent of type, then this will probably seem ridiculous to you.
Have you ever wondered why everyone else swears by temperament theory, and think it adequately explains things, while to you it seems kind of like an arbitrary boundary between things that don't seem mutually exclusive?
Well, I have an answer. Look at this:
There are several reasons why INJs are left as outliers. The chief reason, is their rarity in the population (the statistics showing that INJs are the rarest types are well-known, so I will not bother to source them). The majority of INxx types are INPs, for whom the system works perfectly. ENJs and ENPs do not generally feel enough of a disparity to question the concept, though they probably feel far less certain about it than INPs. It really only affects INJs, thus the tool was built around handling the most common situation.
I feel I should also note that the creator of MBTI herself, Isabel Myers, was an INFP, and hence saw things from an INFP perspective. David Keirsey, another major proponent of temperament theory, was an INTP. Therefore, not only was the data based on majority of Intuitives tested, who were not INJs, but the designers of the system themselves were INPs, and thus saw things from an INP perspective. I'm not saying that they were deliberately biased, however. In fact, even if they saw this disparity, there might have been no way to fix the system for INJs without making it less helpful for the majority of Intuitives. I do think that it should have been noted, however.
Now, Keirsey clearly realized some of the issues with dividing people who have the SAME dominant function, at least among Sensors. It was this sense that lead him to create temperaments that would group together both ESPs and both ISJs, yet he actually created a new problem by placing both ESJs and both ISPs into the same temperaments, destroying the ST and SF temperaments for those who found them most useful. Perhaps his experiences involved more ESPs and ISJs, so he felt compelled to repair the situation for them? I don't know.
What I do know, is that this issue is created by attempting to reduce Jungian theory into something similar to the ancient four temperament system Galen came up with (Sanguine, Melancholy, Choleric, Phlegmatic). I believe that doing so is actually a mistake. Jung (his type is debated, but my ego would like to believe he was an INFJ) would never have done this, and I doubt he would have condoned it when Isabel and Keirsey did it. In Jungian theory, a person's basic type IS their dominant function, and the auxiliary is a balancing function that a person has a much weaker preference for in general. The fact that most people acknowledge that it doesn't even start developing until age 12, is a fairly good indicator that it's not at the core of a person's psyche, and does not define them the way a dominant function does.
Now, I believe that the motivation in doing this, was to describe how types generally appear to other people, as the J/P dichotomy attempts to do. Not to describe their underlying motivations. In this, it is partly successful, but often assigns people incorrectly due to being grossly incongruent with the underlying system.
My suggestion to everyone is this... pay careful attention to functions and individual type descriptions. Do not type yourself using temperament theory, because it often uses strong stereotypes... it could well make a person in academia or intellectual subjects think they're an NT, a person in business or theology think they're an SJ, and a social worker or "emo" person think they're an NF. The archetypes implied by them are quite superficial, and usually not representative of underlying psychology. Jung is probably turning over in his grave every time people rely on it to type themselves or validate their typing.
Note that I have made three basic assumptions while writing this:
1. Dominant functions filter the flavor of all the functions below them.
2. Function strength is largely decided by type. There can be slight variations, but not major ones. If there are major ones, you belong to a different type.
3. Introverted functions are felt a little more strongly as part of the self, if placed in the dominant or auxiliary positions.
I apologize if this thread has been created before... I wasn't able to find it using a search, and the idea has occurred to me several times.
This issue may in fact disappear to some extent with INJs who extravert themselves a lot, and make heavy use of the auxiliary such that they come to identify with it almost as much as Ni. This is especially true if they leave their tertiary function relatively undeveloped. However, I think that these INJs tend to be more the exception than the rule (though INJs seem to be the exception to MOST rules anyway).