[MENTION=16826]Tessertime[/MENTION] and [MENTION=16748]Il Morto Che Parla[/MENTION] both of you fellas are having a very intriguing discussion here that threatens to fissure the foundations of the whole typology theory since you brought up the ever changing state of the brain and how these functions such as Ni that folk so dearly desire have poor definitions which lack sufficent empirically gathered data to prove their validity is what I am gathering. Keep this conversation going my friends!
I was once a strong advocate for MBTI. But that was before I expanded my knowledge-banks to neuroscience, not to mention my own collective research on the functions. Now, I put forward the proposition that typology is an inaccurate, and rather flawed, theory that attempts to simplify a very complex and diverse system that has only recently been explored in-depth within the mid to late 90's (you could even pinpoint rapid advances to the early 2000's) and we still don't know much!
A theory is a theory if it follows two distinctive traits:
(1) It must accurately describe a large class of observations on the basis of a model, and
(2) It must make definite predictions about the results of future observations.
These are generally held to standard in physics, but I don't see why it couldn't hold weight to theories in other scientific fields.
MBTI often has a hard time meeting those two criteria.
Typology theories, like MBTI to use as the prime example here (most familiar with) attempts to configure personalities that overlap, and often contradict, the core of each established identity. I could point out that the brain is a complex system of chemical and electrical reactions/impulses, ones that can be quantized, and would therefore fit in to the uncertainty principle. If you wanted to expand the uncertainty principle to a larger concept, you could propose that the more you attempt to define and pinpoint a person's personality, the less certain you can predict how it is moving. On the flip side, the more you attempt to predict where a person's personality is going, the less certain you can predict where it is at.
That may be entirely untrue though, as quantum mechanics is quantized, whereas in physics the level of personalities would fall under the threshold of General Relativity (if the only connection to General Relativity is the abstract view.) But I wouldn't the uncertainty principle maintains an important connection to personalities.
Furthermore, in the realms of neuroscience, the brain's structure can change over time, which then presents the dilemna of fixated personalities. Some neuroscientists and psychologists have argued against typology as the changing structure can throw typology into realms of questionable limits.
To add to the frustration is a myriad of subjective definitions of each function, with a unified definitization of each function non-existent, if not entirely vague. Few people like to refer to Jung, as his results are questionable. Even Myers's results could be questioned.
Edit - You can't discount that people like MBTI because it does have aspects of simplicity to it, and can be used with some ease. It is like comparing Newton's Laws to Einstein's General Relativity: Newton's laws, like gravity for example, have proven inaccurate, but it is also easy to use and not
fully innacurate! General Relativity is far more precise, but Newtons's is not too shabby.
It is interesting to hear about, and discuss, the different angles of the theory of MBTI.