Say what? The passage you quoted is Jung describing introverted thinking. It has nothing to do with "Ni and Si types" or the auxiliary function.
Originally Posted by Mal+
It comes near the start of Jung's discussion of extraverted thinking. To put Te in context, he digresses for two paragraphs and offers a mini-introduction to Ti. Here are those paragraphs in full:
Although I do not propose to discuss the nature of introverted thinking at this point, reserving it for a later section (pars. 628-31), it is essential that I should say a few words about it before proceeding further. For if one reflects on what I have just said about extraverted thinking, one might easily conclude that this covers everything that is ordinarily understood as thinking. A thinking that is directed neither to objective facts nor to general ideas, one might argue, scarcely deserves the name "thinking" at all. I am fully aware that our age and its most eminent representatives know and acknowledge only the extraverted type of thinking. This is largely because all the thinking that appears visibly on the surface in the form of science or philosophy or even art either derives directly from objects or else flows into general ideas. For both these reasons it appears essentially understandable, even though it may not always be self-evident, and it is therefore regarded as valid. In this sense it might be said that the extraverted intellect oriented by objective data is actually the only one that is recognized. But—and now I come to the question of the introverted intellect—there also exists an entirely different kind of thinking, to which the term "thinking" can hardly be denied: it is a kind that is oriented neither by immediate experience of objects nor by traditional ideas. I reach this other kind of thinking in the following manner: when my thoughts are preoccupied with a concrete object or a general idea, in such a way that the course of my thinking eventually leads me back to my starting-point, this intellectual process is not the only psychic process that is going on in me. I will disregard all those sensations and feelings which become noticeable as a more or less disturbing accompaniment to my train of thought, and will merely point out that this very thinking process which starts from the object and returns to the object also stands in a constant relation to the subject. This relation is a sine qua non, without which no thinking process whatsoever could take place. Even though my thinking process is directed, as far as possible, to objective data, it is still my subjective process, and it can neither avoid nor dispense with this admixture of subjectivity. Struggle as I may to give an objective orientation to my train of thought, I cannot shut out the parallel subjective process and its running accompaniment without extinguishing the very spark of life from my thought. This parallel process has a natural and hardly avoidable tendency to subjectify the objective data and assimilate them to the subject.
Now when the main accent lies on the subjective process, that other kind of thinking arises which is opposed to extraverted thinking, namely, that purely subjective orientation which I call introverted. This thinking is neither determined by objective data nor directed to them; it is a thinking that starts from the subject and is directed to subjective ideas or subjective facts. I do not wish to enter more fully into this kind of thinking here; I have merely established its existence as the necessary complement of extraverted thinking and brought it into clearer focus.