There is the Jung original description. I dont think Jung appreciated Ti that much. Here it goes:
A verbatim excerpt taken from Chapter 10 of Carl Gustav Jung's work "Psychological Types" (1921):
=============================================
(III) PECULIARITIES OF THE BASIC PSYCHOLOGICAL FUNCTIONS IN THE INTROVERTED ATTITUDE
1. Thinking
When describing extraverted thinking, I gave a brief characterization of introverted thinking, to which at this stage I must make further reference. Introverted thinking is primarily orientated by the subjective factor. At the least, this subjective factor is represented by a subjective feeling of direction, which, in the last resort, determines judgment. Occasionally, it is a more or less finished image, which to some extent, serves as a standard. This thinking may be conceived either with concrete or with abstract factors, but always at the decisive points it is orientated by subjective data. Hence, it does not lead from concrete experience back again into objective things, but always to the subjective content, External facts are not the aim and origin of this thinking, although the introvert would often like to make it so appear. It begins in the subject, and returns to the subject, although it may [p. 481] undertake the widest flights into the territory of the real and the actual. Hence, in the statement of new facts, its chief value is indirect, because new views rather than the perception of new facts are its main concern. It formulates questions and creates theories; it opens up prospects and yields insight, but in the presence of facts it exhibits a reserved demeanour. As illustrative examples they have their value, but they must not prevail. Facts are collected as evidence or examples for a theory, but never for their own sake. Should this latter ever occur, it is done only as a compliment to the extraverted style. For this kind of thinking facts are of secondary importance; what, apparently, is of absolutely paramount importance is the development and presentation of the subjective idea, that primordial symbolical image standing more or less darkly before the inner vision. Its aim, therefore, is never concerned with an intellectual reconstruction of concrete actuality, but with the shaping of that dim image into a resplendent idea. Its desire is to reach reality; its goal is to see how external facts fit into, and fulfil, the framework of the idea; its actual creative power is proved by the fact that this thinking can also create that idea which, though not present in the external facts, is yet the most suitable, abstract expression of them. Its task is accomplished when the idea it has fashioned seems to emerge so inevitably from the external facts that they actually prove its validity.
But just as little as it is given to extraverted thinking to wrest a really sound inductive idea from concrete facts or ever to create new ones, does it lie in the power of introverted thinking to translate its original image into an idea adequately adapted to the facts. For, as in the former case the purely empirical heaping together of facts paralyses thought and smothers their meaning, so in the latter case introverted thinking shows a dangerous tendency [p. 482] to coerce facts into the shape of its image, or by ignoring them altogether, to unfold its phantasy image in freedom. In such a case, it will be impossible for the presented idea to deny its origin from the dim archaic image. There will cling to it a certain mythological character that we are prone to interpret as 'originality', or in more pronounced cases' as mere whimsicality; since its archaic character is not transparent as such to specialists unfamiliar with mythological motives. The subjective force of conviction inherent in such an idea is usually very great; its power too is the more convincing, the less it is influenced by contact with outer facts. Although to the man who advocates the idea, it may well seem that his scanty store of facts were the actual ground and source of the truth and validity of his idea, yet such is not the case, for the idea derives its convincing power from its unconscious archetype, which, as such, has universal validity and everlasting truth. Its truth, however, is so universal and symbolic, that it must first enter into the recognized and recognizable knowledge of the time, before it can become a practical truth of any real value to life. What sort of a causality would it be, for instance, that never became perceptible in practical causes and practical results?
This thinking easily loses itself in the immense truth of the subjective factor. It creates theories for the sake of theories, apparently with a view to real or at least possible facts, yet always with a distinct tendency to go over from the world of ideas into mere imagery. Accordingly many intuitions of possibilities appear on the scene, none of which however achieve any reality, until finally images are produced which no longer express anything externally real, being 'merely' symbols of the simply unknowable. It is now merely a mystical thinking and quite as unfruitful as that empirical thinking whose sole operation is within the framework of objective facts. [p. 483]
Whereas the latter sinks to the level of a mere presentation of facts, the former evaporates into a representation of the unknowable, which is even beyond everything that could be expressed in an image. The presentation of facts has a certain incontestable truth, because the subjective factor is excluded and the facts speak for themselves. Similarly, the representing of the unknowable has also an immediate, subjective, and convincing power, because it is demonstrable from its own existence. The former says 'Est, ergo est' ('It is ; therefore it is') ; while the latter says 'Cogito, ergo cogito' (' I think ; therefore I think'). In the last analysis, introverted thinking arrives at the evidence of its own subjective being, while extraverted thinking is driven to the evidence of its complete identity with the objective fact. For, while the extravert really denies himself in his complete dispersion among objects, the introvert, by ridding himself of each and every content, has to content himself with his mere existence. In both cases the further development of life is crowded out of the domain of thought into the region of other psychic functions which had hitherto existed in relative unconsciousness. The extraordinary impoverishment of introverted thinking in relation to objective facts finds compensation in an abundance of unconscious facts. Whenever consciousness, wedded to the function of thought, confines itself within the smallest and emptiest circle possible -- though seeming to contain the plenitude of divinity -- unconscious phantasy becomes proportionately enriched by a multitude of archaically formed facts, a veritable pandemonium of magical and irrational factors, wearing the particular aspect that accords with the nature of that function which shall next relieve the thought-function as the representative of life. If this should be the intuitive function, the 'other side' will be viewed with the eyes of a Kubin or a Meyrink. If it is the feeling-function, [p. 484] there arise quite unheard of and fantastic feeling-relations, coupled with feeling-judgments of a quite contradictory and unintelligible character. If the sensation-function, then the senses discover some new and never-before-experienced possibility, both within and without the body. A closer investigation of such changes can easily demonstrate the reappearance of primitive psychology with all its characteristic features. Naturally, the thing experienced is not merely primitive but also symbolic; in fact, the older and more primeval it appears, the more does it represent the future truth: since everything ancient in our unconscious means the coming possibility.
Under ordinary circumstances, not even the transition to the 'other side' succeeds -- still less the redeeming journey through the unconscious. The passage across is chiefly prevented by conscious resistance to any subjection of the ego to the unconscious reality and to the determining reality of the unconscious object. The condition is a dissociation-in other words, a neurosis having the character of an inner wastage with increasing brain-exhaustion -- a psychoasthenia, in fact.
2. The Introverted Thinking Type
Just as Darwin might possibly represent the normal extraverted thinking type, so we might point to Kant as a counter-example of the normal introverted thinking type. The former speaks with facts; the latter appeals to the subjective factor. Darwin ranges over the wide fields of objective facts, while Kant restricts himself to a critique of knowledge in general. But suppose a Cuvier be contrasted with a Nietzsche: the antithesis becomes even sharper.
The introverted thinking type is characterized by a priority of the thinking I have just described. Like his [p. 485] extraverted parallel, he is decisively influenced by ideas; these, however, have their origin, not in the objective data but in the subjective foundation. Like the extravert, he too will follow his ideas, but in the reverse direction: inwardly not outwardly. Intensity is his aim, not extensity. In these fundamental characters he differs markedly, indeed quite unmistakably from his extraverted parallel. Like every introverted type, he is almost completely lacking in that which distinguishes his counter type, namely, the intensive relatedness to the object. In the case of a human object, the man has a distinct feeling that he matters only in a negative way, i.e., in milder instances he is merely conscious of being superfluous, but with a more extreme type he feels himself warded off as something definitely disturbing. This negative relation to the object-indifference, and even aversion-characterizes every introvert; it also makes a description of the introverted type in general extremely difficult. With him, everything tends to disappear and get concealed. His judgment appears cold, obstinate, arbitrary, and inconsiderate, simply because he is related less to the object than the subject. One can feel nothing in it that might possibly confer a higher value upon the object; it always seems to go beyond the object, leaving behind it a flavour of a certain subjective superiority. Courtesy, amiability, and friendliness may be present, but often with a particular quality suggesting a certain uneasiness, which betrays an ulterior aim, namely, the disarming of an opponent, who must at all costs be pacified and set at ease lest he prove a disturbing- element. In no sense, of course, is he an opponent, but, if at all sensitive, he will feel somewhat repelled, perhaps even depreciated. Invariably the object has to submit to a certain neglect; in worse cases it is even surrounded with quite unnecessary measures of precaution. Thus it happens that this type tends to [p. 486] disappear behind a cloud of misunderstanding, which only thickens the more he attempts to assume, by way of compensation and with the help of his inferior functions, a certain mask of urbanity, which often presents a most vivid contrast to his real nature. Although in the extension of his world of ideas he shrinks from no risk, however daring, and never even considers the possibility that such a world might also be dangerous, revolutionary, heretical, and wounding to feeling, he is none the less a prey to the liveliest anxiety, should it ever chance to become objectively real. That goes against the grain. When the time comes for him to transplant his ideas into the world, his is by no means the air of an anxious mother solicitous for her children's welfare; he merely exposes them, and is often extremely annoyed when they fail to thrive on their own account. The decided lack he usually displays in practical ability, and his aversion from any sort of re[accent]clame assist in this attitude. If to his eyes his product appears subjectively correct and true, it must also be so in practice, and others have simply got to bow to its truth. Hardly ever will he go out of his way to win anyone's appreciation of it, especially if it be anyone of influence. And, when he brings himself to do so, he is usually so extremely maladroit that he merely achieves the opposite of his purpose. In his own special province, there are usually awkward experiences with his colleagues, since he never knows how to win their favour; as a rule he only succeeds in showing them how entirely superfluous they are to him. In the pursuit of his ideas he is generally stubborn, head-strong, and quite unamenable to influence. His suggestibility to personal influences is in strange contrast to this. An object has only to be recognized as apparently innocuous for such a type to become extremely accessible to really inferior elements. They lay hold of him from the [p. 487] unconscious. He lets himself be brutalized and exploited in the most ignominious way, if only he can be left undisturbed in the pursuit of his ideas. He simply does not see when he is being plundered behind his back and wronged in practical ways: this is because his relation to the object is such a secondary matter that lie is left without a guide in the purely objective valuation of his product. In thinking out his problems to the utmost of his ability, he also complicates them, and constantly becomes entangled in every possible scruple. However clear to himself the inner structure of his thoughts may be, he is not in the least clear where and how they link up with the world of reality. Only with difficulty can he persuade himself to admit that what is clear to him may not be equally clear to everyone. His style is usually loaded and complicated by all sorts of accessories, qualifications, saving clauses, doubts, etc., which spring from his exacting scrupulousness. His work goes slowly and with difficulty. Either he is taciturn or he falls among people who cannot understand him; whereupon he proceeds to gather further proof of the unfathomable stupidity of man. If he should ever chance to be understood, he is credulously liable to overestimate. Ambitious women have only to understand how advantage may be taken of his uncritical attitude towards the object to make an easy prey of him; or he may develop into a misanthropic bachelor with a childlike heart. Then, too, his outward appearance is often gauche, as if he were painfully anxious to escape observation; or he may show a remarkable unconcern, an almost childlike naivete. In his own particular field of work he provokes violent contradiction, with which he has no notion how to deal, unless by chance he is seduced by his primitive affects into biting and fruitless polemics. By his wider circle he is counted inconsiderate and domineering. But the [p. 488] better one knows him, the more favourable one's judgment becomes, and his nearest friends are well aware how to value his intimacy. To people who judge him from afar he appears prickly, inaccessible, haughty; frequently he may even seem soured as a result of his anti-social prejudices. He has little influence as a personal teacher, since the mentality of his pupils is strange to him. Besides, teaching has, at bottom, little interest for him, except when it accidentally provides him with a theoretical problem. He is a poor teacher, because while teaching his thought is engaged with the actual material, and will not be satisfied with its mere presentation.
With the intensification of his type, his convictions become all the more rigid and unbending. Foreign influences are eliminated; he becomes more unsympathetic to his peripheral world, and therefore more dependent upon his intimates. His expression becomes more personal and inconsiderate and his ideas more profound, but they can no longer be adequately expressed in the material at hand. This lack is replaced by emotivity and susceptibility. The foreign influence, brusquely declined from without, reaches him from within, from the side of the unconscious, and he is obliged to collect evidence against it and against things in general which to outsiders seems quite superfluous. Through the subjectification of consciousness occasioned by his defective relationship to the object, what secretly concerns his own person now seems to him of chief importance. And he begins to confound his subjective truth with his own person. Not that he will attempt to press anyone personally with his convictions, but he will break out with venomous and personal retorts against every criticism, however just. Thus in every respect his isolation gradually increases. His originally fertilizing ideas become destructive, because poisoned by a kind of sediment of bitterness. His struggle against the influences emanating [p. 489] from the unconscious increases with his external isolation, until gradually this begins to cripple him. A still greater isolation must surely protect him from the unconscious influences, but as a rule this only takes him deeper into the conflict which is destroying him within.
The thinking of the introverted type is positive and synthetic in the development of those ideas which in ever increasing measure approach the eternal validity of the primordial images. But, when their connection with objective experience begins to fade, they become mythological and untrue for the present situation. Hence this thinking holds value only for its contemporaries, just so long as it also stands in visible and understandable connection with the known facts of the time. But, when thinking becomes mythological, its irrelevancy grows until finally it gets lost in itself. The relatively unconscious functions of feeling, intuition, and sensation, which counterbalance introverted thinking, are inferior in quality and have a primitive, extraverted character, to which all the troublesome objective influences this type is subject to must be ascribed. The various measures of self-defence, the curious protective obstacles with which such people are wont to surround themselves, are sufficiently familiar, and I may, therefore, spare myself a description of them. They all serve as a defence against 'magical' influences; a vague dread of the other sex also belongs to this category.
[ Web Source: Classics in the History of Psychology -- Jung (1921/1923) Chapter 10 ]
=============================================
From:
[ISTP] Jung's Description of the Introverted Thinking Type (Ti-dominant)
