In my travels around this message board and my interactions with others and my endless inner speculation on the various ways of interpreting them, I believe I've discovered a few things.
I became interested in MBTI because I liked the way it allowed me to see past my own personal biases by conceptualizing the behavioral attitudes of myself and others in terms of a theoretical, impersonal logic system. Since that's pretty much how I approach everything in my head, it was simultaneously humbling and fantastically interesting to finally be able to label and categorize (dare I say understand?) the highly complex game that is interpersonal interaction. I loved the way it could succinctly sum up quite a few behaviors in just a few words--at last, I'd found an overarching theory to summarize (at least partially) a wide range of varying and confusing data in a rationally consistent manner.
I used to just dismiss every viewpoint that conflicted with mine as illogical, stupid and therefore inferior--until I finally stepped back and realized that hard logic is not the only value system in play, and more importantly, that maintaining logical dominance was not worth sacrificing the numerous benefits of approaching life's many situations with a variety of value systems. I'd been applying the same strategy to every situation, and naively convincing myself that no other strategy was worth paying any attention to. Boy, was I wrong.
It's illogical to hold everyone else to a logical standard, I discovered.
But upon joining this forum and beginning to post and read posts by others, I found that many people seemed to be vastly overestimating the predictive abilities of such a simple system. MBTI is useful when taken for what it is and nothing more: a vague and very general description of four behavioral attitudes and preferences which happen to coincide meaningfully with a number of common externalized behaviors.
It's not really anything new or groundbreaking--it's just grouping similar behaviors in people and giving an arbitrary name to the internal assumptions about others that we all constantly make every day. He's a know-it-all; she's such a control freak; he's so whimsical. At the end of the day, it's nothing more than a sophisticated method of name-calling.
So where does this cognitive function thing come in? How do we make the leap from grouping behaviors and using them to predict similar behaviors in similar situations to actually explaining the internal cognitive processes that result in these behavioral attitudes?
Where does "Bob is a J because he prefers having a plan more often than not" get translated into such amateur psychoanalysis as, "Bob is motivated toward this preference by his Xi function (whose very existence is highly speculative and totally unsubstantiated)"?
How do you know?
I've been told repeatedly that I should forget profiles and change my approach to just functions, and after listening to several people explain the merits of such an approach I must say I disagree wholeheartedly. To make such a claim is to vastly overestimate the value of typology.
It seems to me there are two ways to look at cognitive functions. One is just a restatement of the four MBTI letters (this is what you're getting if you take a so-called "cognitive functions test"), and the other is waaaay overstepping its boundaries in terms of predictive ability.
When I read descriptions of the cognitive functions, I can't help but wonder how anyone could even hope to associate them with particular actions or behaviors in themselves, much less in others. That requires so many more levels of depth of understanding of another person's psyche than is even remotely possible for an outsider that the entire cognitive function system has yet to convince me that it has any value beyond that of a cute guessing game.
It sure would be nice to be able to explain the entirety of human psychology in such a neat little eight-piece box, but that's frankly unrealistic, and anyone who believes otherwise is simply delusional. Any behavior can be caused by any function, and in reality is likely caused by numerous functions acting in concert. This can take so many different forms and appearances, and moreover is SO person-dependent, that functional theory has little to no value in the absence of firsthand information and subjective experience.
And yet, proponents of Jung's functional theory truly believe they can accurately and reliably perceive, dissect and properly interpret the internal motivations for virtually everything everyone does. Sure, MBTI is based on Jung's theories, but it's also developed into a separate and mutually exclusive system. Prince is a Jehovah's witness; that doesn't mean I have to be in order to appreciate his work. Jung may have had a few good ideas that later served as the basis for MBTI, but he was by no means consistently reliable--I mean, the man believed in astrology, for fuck's sake.
Try taking him with a little bigger grain of salt! As always I'm reminded of the parallels with poker:
MBTI looks at a player, notices that he seems to bet in situation x more often than not, and makes a mental note that he probably prefers betting in situation x. This implies that he may also bet in similar situation y, but makes no attempt at explaining the unconscious internal motivations for why he bets this way.
Jungian functional theory looks at a player, notices that he seems to bet in situation x more often than not, and then declares with impunity that he does this because he has an unconscious need to win every pot where situation x occurs in order to prop up his fragile self-esteem.
Can you spot the difference?!
I, for one, think Keirsey had it juuuust right--anything beyond categorization of behavioral attitudes, and you've wandered right over the line into purely speculative pop-psychology drivel. You can speculate as to internal psychological motivations until the cows come home, but without experiencing life through the eyes of another person, you simply do not have the data necessary to make any kind of useful functional assessment of others at all.
There's a reason MBTI is taught in college psychology and business management courses, and Jung is not. If you think the four-variable system is too simplistic or otherwise inferior, it's because you expect typology to do more than it can reasonably be expected to.
Hate to bruise egos here, but you are not "reading functions" in others any more than Taurus with a Virgo rising (or wtfever) is influencing human behavior--no matter how skilled you may be at twisting the data to trick yourself into making it seem internally consistent.