The whole of my research work for the last years has been concentrated upon this question. The first stage of this work was to discover the extent to which the two theories discussed above were tenable. The second stage consisted in the recognition of the fact, that these two theories correspond to two opposite psychological types, which I have designated the introversion and the extroversion types. William James[237] was struck by the existence of these two types among thinkers. He differentiated them as the "tough-minded," and the "tender-minded." Similarly, Ostwald[238] discovered an analogous difference in the classical and romantic types among great scholars. I am not therefore alone in my ideas about the types, as is testified by mentioning only these two well-known names out of many others. Historical researches have proved to me that not a few of the great controversies in the history of thought were based upon the contrast between the types. The most significant case of this kind is the contrast between nominalism and realism, which, beginning with the difference between the Platonic and the Megarian schools, descended to scholastic philosophy, where Abelard won the immortal distinction of at least having ventured an attempt to unite the two contradictory standpoints in conceptualism. This conflict has continued down to the present day, where it finds expression in the antagonism of spiritualism and materialism.
Just as in the general history of thought, so too every individual has a share in this contrast of types. Close investigation proves that people of opposite types have an unconscious predilection for marrying each other, that they may mutually complement one another. Each type has one function that is specially well developed, the introvert using his thought as the function of adaptation, thinking beforehand about how he shall act; whilst the extrovert, on the contrary, feels his way into the object by acting. To some extent he acts beforehand. Hence by daily application the one has developed his thought, and the other his feeling. In extreme cases the one limits himself to thinking and observing, and the other to feeling and acting. It is true that the introvert feels also, very deeply indeed, almost too deeply; that is why an English investigator[239] has gone so far as to describe his as "the emotional type." True, the emotion is there, but it all remains inside, and the more passionate and deeper his feeling is, the quieter is his outward demeanour. As the proverb puts it, "Still waters run deep." Similarly, the extrovert thinks also, but that likewise mostly inside, whilst his feelings visibly go outside, that is why he is held to be full of feeling whilst the introvert is considered cold and dry. But as the feeling of the thinker goes inwards, it is not developed as a function adapted to external situations, but remains in a relatively undeveloped state. Similarly the thinking of one who feels remains also relatively undeveloped.
But if comparatively well-adapted individuals are under consideration, then the introvert will normally be found to have his feeling directed outwards, and the result may be extraordinarily deceptive. He shows feelings; he is amiable, sympathetic, even emotional. But a critical examination of the expressions of his feelings reveals that they are markedly conventional. They are not individualised. He shows to every one, without any essential difference, the same friendliness and the same sympathy; whilst the extrovert's expressions of feeling are throughout delicately graded and individualised. With the introvert the expression of feelings is really a gesture that is artificially adopted and conventional. Similarly, the extrovert may apparently think, and that even very clearly and scientifically. But upon closer investigation, his thoughts are found to be really foreign property, merely conventional forms which have been artificially acquired. They lack anything individual and original, and are just as lukewarm and colourless as the conventional feelings of the introvert. Under these conventional disguises, quite other things are slumbering in both, which occasionally when awakened by some overpowering effect, suddenly break out to the astonishment and horror of the environment.
Most civilised people incline more to one type than the other. Taken together they would supplement each other exceedingly well. That is why they are so apt to marry one another, and so long as they are fully occupied with adapting themselves to the necessities of life they suit one another splendidly. But if the man has earned a competence, or if a big legacy drop from the sky, terminating the external urgencies of life, then they have time to occupy themselves with each other. Until now they stood back to back, defending themselves against want. But now they turn to each other expecting to understand one another; and they make the discovery that they have never understood one another. They speak different languages. Thus the conflict between the two types of psychology begins. This conflict is venomous, violent and full of mutual depreciation, even if it be conducted very quietly in the utmost intimacy. This is so because the value of the one is the worthlessness of the other. The one, starting from the standpoint of his valuable thinking, takes for granted that the feelings of the other correspond to his own inferior feelings, this because he knows absolutely nothing of any other feelings. But the other, starting from the standpoint of his valuable feelings, assumes that his partner has the same inferior thought that he himself has. Evidently there is plenty of work here for Goethe's Homunculus, who had to find out "why husband and wife get on so badly." Now as many cases of neurosis have a basis in such differences, I, as a physician, found myself obliged to relieve the Homunculus of some of his ungrateful task. I am glad to be able to say that many a sufferer has been helped in grave difficulties by the enlightenment I could give.
The third stage of the path of increasing understanding consisted in formulating a theory of the psychology of types which would be of practical use for the development of man. Viewed from the newly-gained standpoint, there resulted, first of all, a totally new theory of psychogenic disturbances.
The foundation of the facts remains the same: the first hypothesis of every neurosis is the existence of an unconscious conflict. According to Freud's theory, this is an erotic conflict, or to speak more exactly, a battle of the moral consciousness against the unconscious infantile sexual world of phantasy and its transference to external objects. According to Adler's theory, it is a battle of the superiority of the ego against all oppressive influences, whether from inside or outside.
But the new idea asserts that the neurotic conflict always takes place between the adapted function and the co-function that is undifferentiated, and that lies to a great extent in the unconscious; therefore in the case of the introvert, between thought and unconscious feeling, but in that of the extrovert, between feeling and unconscious thought.[240] Another theory of the etiological moment results from this. If a man who naturally adapts himself by thinking is faced by a demand that cannot be met by thinking alone, but which requires differentiated feeling, the traumatic or pathogenic conflict breaks out. On the contrary, the critical moment comes to the man who adapts by feeling when he is faced by a problem requiring differentiated thought. The afore-mentioned case of the business man is a clear example of this. The man was an introvert, who all through his life had left every consideration of sentiment in the background, that is, in the unconscious. But when, for the first time in his life, he found himself in a situation in which nothing could be done except by means of differentiated feeling, he failed utterly. At the same time, a very instructive phenomenon occurred; his unconscious feelings manifested themselves as physical sensations of a vague nature. This fact harmonises with a generally accepted experience in our psychology, to wit, that undeveloped feelings partake of the character of vague physical sensations, since undifferentiated feelings are as yet identical with subjective physical sensations. Differentiated feelings are of a more "abstract" objective nature. This phenomenon may well be the unconscious basis of the earliest statement of psychological types that is known to me; namely, the three types of the Valentinian School. They held the undifferentiated type to be the so-called hylic (material) man. He was ranked below the differentiated types, that is, the psychic (soulful) man, who corresponds to the extroversion type; and the pneumatic (spiritual) man, who corresponds to the introversion type. For these gnostics the "pneumatikos" stood of course the highest. Christianity, with its "psychic" (spiritual) nature (principle of love), has indeed contested this privilege of the gnosis. But even this page may be turned in the course of time: since, if the signs of the age are not deceptive, we are now in the great final settlement of the Christian epoch. We know that, evolution not being uniformly continuous, when one form of creation has been outlived, the evolutionary tendency harks back to resume that form which, after having made a beginning, was left behind in an undeveloped state.
After this brief digression to generalities, let us return to our case. If a similar disturbance were to take place in an extrovert, he would have what are called hysterical symptoms, that is, symptoms that are also of an apparently physical nature, which, as our theory indicates, would this time represent the patient's unconscious undifferentiated thought. As a matter of fact, we find also a widespread region of phantasy as the basis of hysterical symptoms, of which many have been described in detail in the literature of the subject. They are phantasies of a pronounced sexual, that is physical complexion. But in reality they are undifferentiated thoughts, which in common with the undifferentiated feelings are to some extent physical, and therefore appear as what may be called physical symptoms.
By taking up again here the thread that was dropped before, we can now clearly see why it is precisely in the neurosis that those values which are most lacking to the individual lie hidden. We might also now return to the case of the young woman, and apply to it the newly-won insight. She is an extrovert with an hysterical neurosis. Let us suppose that this patient had been "analysed," that is, that the treatment having made it clear to her what kind of unconscious thoughts lay behind her symptoms, she had regained possession of the psychic energy which by becoming unconscious had constituted the strength of the symptoms. The following practical question now arises: what can be done with the so-called available energy? It would be rational, and in accordance with the psychological type of the invalid, to extrovert this energy again, that is to transfer it to an object, as for instance to philanthropic or some other useful activities. This way is possible only in exceptional cases—there are energetic natures who do not shrink from care and trouble in a useful cause, there are people who care immensely about just such occupations—otherwise it is not feasible. For it must not be forgotten, that in the case under consideration, the libido (that is the technical expression for the psychic energy) has found its object already unconsciously in the young Italian, or an appropriate real human substitute. Under these circumstances such a desirable sublimation, however natural, is out of the question. For the object of the energy usually affords a better channel than an ethical activity, however attractive. Unfortunately there are many people who always speak of a person, not as he is, but as he would be if their desires for him were realised. But the physician is necessarily concerned with the actual personality, which will obdurately remain the same, until its real character has been recognised on all sides. An analysis must necessarily be based upon the recognition of naked reality, not upon any arbitrarily selected phantasies about a person, however desirable.