Some ideas of Jung

I must confess, I have never read completely through Jung's Psychological Types, or even the chapter that is about the type definitions. I find the writing to be often convoluted and not very much related to socionics as it stands today. Perhaps the best part is the description of extroversion and introversion:

"The relation between subject and object, considered biologically, is always a relation of adaptation, since every relation between subject and object presupposes mutually modifying effects from either side. These modifications constitute the adaptation. The typical attitudes to the object, therefore, are adaptation processes. Nature knows two fundamentally different ways of adaptation, which determine the further existence of the living organism the one is by increased fertility, accompanied by a relatively small degree of defensive power and individual conservation; the other is by individual equipment of manifold means of self-protection, coupled with a relatively insignificant fertility. This biological contrast seems not merely to be the analogue, but also the general foundation of our two psychological modes of adaptation, At this point a mere general indication must suffice; on the one hand, I need only point to the peculiarity of the extravert, which constantly urges him to spend and propagate himself in every way, and, on the other, to the tendency of the introvert to defend himself against external claims, to conserve himself from any expenditure of energy directly related to the object, thus consolidating for himself the most secure and impregnable position."

That is, maintaining vs. propagating the self. This fits completely with socionics extro/introversion, and in particular Si and Se.

However, Jung later published a much shorter pamphlet on his personality types called "A Psychological Theory of Types" (1931). The full text does not seem to be online anywhere except on Google Books. In it, Jung describes some concepts that are very important for socionics. He realizes the importance of the "compass" of personality, which has Intuition, Feeling, Sensing, and Thinking at its four corners, each function across from its opposite. In socionics this forms what we would call a supervision ring or benefit ring, since each of the leading functions of the types in the ring must correspond to these four categories.

"The four functions are somewhat like the four points of the compass; they are just as arbitrary and just as indispensable.

Nothing prevents our shifting the cardinal points as many degrees as we like in one direction or the other, or giving them different names.

It is merely a question of convention and intelligibility.

But one thing I must confess: I would not for anything dispense with this compass on my psychological voyages of discovery. This is not merely for the obvious, all-too-human reason that everyone is in love with his own ideas. I value the type theory for the objective reason that it provides a system of comparison and orientation which makes possible something that has long been lacking, a critical psychology."

Instead of "critical psychology" we may say: a mathematical, structural theory of the self.

This compass is the crux behind socionics and indeed reality itself. Although it may seem attractive, any attempt to found socionics purely based on dichotomies (and in ignorance of the relationship group) seems to me doomed to fail. That is because it does not acknowledge the geometric transition between discrete traits that is given by the continuous rotation of the square.

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Jung says regarding psychiatry: "Its concepts are lacking, facts are not; on the contrary, we are surrounded—almost buried—by facts."

This is exactly the situation we still find ourselves in with socionics. While of course it would be desirable to have a way to mechanistically ("empirically") verify the facts of socionics, this is not within the realm of possibility at the moment. What we need now is conceptual clarity and rigorous definitions.

Jung also offers some prescient definitions:

"Just as extraverted sensation strives to reach the highest pitch of actuality, because only thus can the appearance of a complete life be created, so intuition tries to encompass the greatest possibilities, since only through the awareness of possibilities is intuition fully satisfied."

"Sensation establishes what is actually present....intuition points to possibilities as to whence it came and whither it is going in a given situation." 

This is in fact exactly how I see sensing and intuition in socionics - actuality vs. possibility, or presence vs. absence. It's something that perhaps got lost in the formulation of socionics.

However, Jung defines thinking as "meaning" and feeling as "value" which is far less clear.