Hey, I don't mean to devalue intuition. After all it is my favorite function! 
It was Jung that first sold me on the value of calling something irrational and this is how he has described intuition and sensation...as irrational functions to the functions thinking and feeling which are rational.
Not to worry. I understand. My decision to object to the term "irrational" was meant as a direct reaction to Jung's own usage. I just worry that it is another one of those "perspectual" terms (in its Jungian usage). I.e., the way the ego works is "rational", the way the unconscious works is "irrational". If anything, I would put this the other way around. The unconscious seems to perceive things more-accurately and completely than the ego. The ego is a "glancer" that looks very briefly at information and decides how to reconstruct it into something familiar and useful to the ego's style of thinking. Lots of room for "misperceiving".
Rational is a woolly word that is often used to mean a lot of different things. It's usually associated with reason, but reasoning doesn't have to have anything to do with truth. Alternatively, we could say that the irrational
lacks reason . . . but does that mean it lacks causality or logic or predictability? I don't know. Just thinking about how to accurately apply rational and irrational to Jung's functions for a couple minutes leaves me with "woolly fever". I just don't think they are the best words to use. They are not innately descriptive (of the functions), but require a specific redefinition or semantic tweak. To my taste, that kind of tweak is inefficient and suggests that better terms could be found.
Of course, that's me thinking like a linguist or poet again.
As for the thinking function, as I've said in the past, I'm not sure it really exists (as Jungians construct it). I think it is merely the "ego-function" as filtered through Jung's era and specific class . . . where it was the embodiment of the way intellectual males identified themselves (and less frequently, intellectual females). Also, many of the lay Jungians I've encountered are always criticizing "thinking types" for being rigid . . . but these critics seems just as rigid to me (and in the same ways). It's all sloppy language that is widely misused and misunderstood.
I'm not saying it is misused and misunderstood by you. You're a very organized and insightful thinker. But many Jungians have no clue what they are talking about. "Thinking Type" has turned into a Jungian put-down . . . and "Intuitive Type" has become a way of branding those who belong to the tribe of Jung. I'm just concerned that these terms have ultimately caused more confusion and harm than they have provided insight.
I used the type system to think about my inner life and my dreams for many years (until very recently). It's not entirely dysfunctional . . . but I felt like a time came when I started to feel that it was holding back my understanding instead of facilitating it. Like using the wrong tool for the job (hammering with a wrench, let's say). Yes, you can drive nails with a wrench . . . but not as easily or precisely as you can with a hammer.
Of course, the time I started to sense this inadequacy was when I started mixing with other Jungians at K. When I saw how screwed up their understanding of the type system was, I realized that I couldn't keep using that same language without sending woolly, mixed messages to those who used the terms so confusedly. Therefore, like a good poet, I decided to find new language, language that better expresses the thing itself, the signified. Of course I'm still in the process of deciding what this might be.
And as for the feeling function, I think there could be a correlation to an unconscious valuation system in the brain that somehow reinforces certain memory connections and consolidations. The connections that get a lot of reinforcement (probably some kind of neurochemical stimulus) are perceived as more valued by our sense of self. Valuating such neuronal connections helps reinforce memory constructs and the complex connectedness of thoughts. But we also experience some kind of emotion in valuation, an approval for certain connections that "feels right". If it feels "really, really right", that feeling could be numinousness. I suspect that such valuations are quantitative and "measurable" by degree of reinforcement.
But here we run into the problem of Jung's specific differentiation between feeling and emotion/affect. If the model I'm suggesting is in some way accurate (and it at least agrees with an element of the Confabulation Theory I posted about elsewhere), then a clear distinction can't really be made between feeling and emotion. That is, not because they are equivalent, but because they are connected, are two elements of one thing: valuation. Emotion is essential and can't be devalued into affect in the conventional Jungian way. Emotion can tell us where value is . . . although not what it is. Emotion isn't "wrong" or inaccurate until it is interpreted through egoic perception. But without this interpretation it is merely a beacon of valuation that homes in on a specific connective structure of memory or thought.
Also, in the construction of feeling above, we have another autonomous, unconscious psychic module in "feeling". Not a conscious one. Just as you said about sensation and intuition. My conclusion is that sensation, intuition, and feeling are all akin to unconscious and autonomous cognitive functions . . . and therefore cannot be considered the "functions of consciousness". Also, this leaves thinking as the "conscious function". Therefore, the "ego-function". Essentially, I think we are all "thinking types" by the Jungian typological system. Thus, when Jungians criticize someone as a "thinking type", they mean that that person is an egoic thinker who holds different beliefs then the critic does.
Of course, to say we are all thinking types is like saying we are all human and conscious. The term becomes worthless. It ceases to describe the actual differences among personalities . . . begging for either a new typological system or some alternative to one.
This is why I feel that Jung's types work better as
functions than they do as personality types. Alternatively, we could say that an "intuitive type" is really just a thinking type that relies more heavily on the function of intuition than any other unconscious function of intelligence. But I'm not sure that construct is really very helpful.
