Carl Gustav Jung
X. General description of the types – 3. The Introverted type, page 345
“As I have already explained in the previous section, the introvert is distinguished from the extravert by the fact that he does not, like the latter, orient himself by the object by objective data, but by subjective factors. I also mentioned that the introvert interposes a subjective view between the perception of the object and his own action, which prevents the action from assuming a character that fits the objective situation. Naturally this is a special instance, mentioned by way of example and intended to serve only as a simple ilustration. We must now attempt a formulation on a broader basis.
Although the introverted consciousness is naturally aware of external conditions, it selects the subjective determinants as the decisive ones. It is therefore oriented by the factor in perception and cognition which responds to the sense stimulus in accordance with the individual’s subjective disposition. For example, two people see the same object, but they never see it in such a way that the images they receive are absolutely identical. Quite apart from the variable acuteness of the sense organs and the personal equation, there often exists a radical difference, both in kind and in degree, in the psychic assimilation of the perceptual image. Whereas the extravert continually appeals to what comes to him from the object, the introvert relies principally appeals to what the sense impression constellates in the subject. The difference in the case of a single apperception may, of course, be very delicate, but in the total psychic economy it makes itself felt in the highest degree, particularly in the effect it has on the ego. If I may anticipate, I consider the viewpoint which inclines, with Weininger, to describe the introverted attitude as philautic, autoerotic, egocentric, subjectivist, egotistic, etc., to be misleading in principle and thoroughly depreciatory. It reflects the normal bias of the extraverted attitude in regard to the nature of the introvert. We must not forget – although the extravert is only too prone to do so – that perception and cognition are not purely objective, but are also subjectively conditioned. The world exist not merely in itself, but also as it appears to me. Indeed, at bottom we have absolutely no criterion that could help us to form a judgment of a world which was unassimilable by the subject. If We were to ignore the subjective factor, It would be a complete denial of the great doubt as to the possibility of absolutely cognition. And this would mean a relapse into the stale and hollow positivism that marred the turn of the century- an attitude of intellectual arrogance accompanied by crudeness of feeling, a violation of life as stupid as it is presumptuous.”