Okay, so what you are saying, is that the only usefulness of MBTI is in the subjective enjoyment in speculating based on the theory? Again, I don't argue with that. I know plenty of people enjoy using it, but that doesn't make understanding the human mind a subjective thing, something that cannot be understood by science. The fact that many people believe astrology is useful, doesn't mean that it's not total crap. It tries to make predictions, so does MBTI as well, and they both utterly fail. What's the point, if there is no validity? By definition it's pure fantasy then.
But that's the thing--when you set up the predictions correctly, they inherently MUST succeed more often than they fail, or you've observed past behavior incorrectly. (Or simply don't have enough data yet to provide any predictive value, in which case you need to keep watching and gradually amend your position.)
Would you agree that we all engage in the process of observing the behavior of others and using it to predict what they will do in the future?
MBTI is simply one system by which to name and categorize these behaviors. It's like saying, "I'm going to arbitrarily label people who tend to like cheese as DFM7 types."
Asking me to prove that they're DFM7 types is missing the point--the entire system's use is subjective because it's defined according to one's own subjective experience. I'm ENTP because I arbitrarily decided that people who follow x, y and z behavioral/attitude patterns are ENTPs. I can't possibly verify this objectively, but I have no reason to even attempt doing so--
at the end of a day, it's just a fancy system of arbitrary name-calling.
It's just that each person's idea of each type is a little different from that of others, based on the unique combination of people in each person's life. The more I talk to other people about it, the more our definitions of ENTP converge as we reach common definitions. Sometimes there are disagreements--nobody is really objectively right or wrong.
We discuss these things to look for common threads between the behaviors of people we know, and the MBTI letters are just a convenient labeling system, a shorthand for the behavioral interactions we all already automatically mentally index and access again and again later on.
You may ask: If it doesn't introduce anything that isn't already there, why bother? To me, that sounds like asking why we use terms like "D flat major" or "Mixolydian" to describe patterns of musical notes. It's simply because organizing it that way mentally makes it easier to conceptualize in certain cases. When I use these terms, I'm not trying to verify scientifically that x, y, z combination of frequencies is called "D flat major"; that isn't the point. It's all an arbitrary label.
MBTI doesn't introduce anything that isn't already there; it's
just an arbitrary categorization system. It's not really intended to be a scientific methodology because there aren't any objective standards for the types--it's just a method of organizing and interpretating the behavior for easier analysis.
Do some people misapply it? Sure, but they're missing the point.
"What's the point if there is no validity?"
hehe. Spoken like a true NTJ. Suffice it to say, consider typology as an art form. All creative fields work with inherently subjective data--as I said, there is no validity to be found in movie reviews, but that doesn't mean the thousands of movie review forums on the internet are wasting their time.
If you go looking for deductive reasoning or objective validity in art, you're missing the point too.