[Carl Jung on Rational and Irrational]

Rational:

Descriptive of thoughts, feelings and actions that accord with reason, an attitude based on objective values established by practical experience.

The rational attitude which permits us to declare objective values as valid at all is not the work of the individual subject, but the product of human history.

Most objective values-and reason itself-are firmly established complexes of ideas handed down through the ages. Countless generations have labored at their organization with the same necessity with which the living organism reacts to the average, constantly recurring environmental conditions, confronting them with corresponding functional complexes, as the eye, for instance, perfectly corresponds to the nature of light. . . . Thus the laws of reason are the laws that designate and govern the average, “correct,” adapted attitude. Everything is “rational” that accords with these laws, everything that contravenes them is “irrational.”[“Definitions,” ibid., par. 785f.]

Jung described the psychological functions of thinking and feeling as rational because they are decisively influenced by reflection.

http://www.nyaap.org/jung-lexicon/r

Irrational:

Not grounded in reason.

Jung pointed out that elementary existential facts fall into this category-for instance, that the earth has a moon, that chlorine is an element or that water freezes at a certain temperature and reaches its greatest density at four degrees centigrade-as does chance. They are irrational not because they are illogical, but because they are beyond reason.

In Jung’s model of typology, the psychological functions of intuition and sensation are described as irrational.

Both intuition and sensation are functions that find fulfilment in the absolute perception of the flux of events. Hence, by their very nature, they will react to every possible occurrence and be attuned to the absolutely contingent, and must therefore lack all rational direction. For this reason I call them irrational functions, as opposed to thinking and feeling, which find fulfillment only when they are in complete harmony with the laws of reason.[Ibid., pars. 776f.]

Merely because [irrational types] subordinate judgment to perception, it would be quite wrong to regard them as “unreasonable.” It would be truer to say that they are in the highest degree empirical. They base themselves entirely on experience. [“General Description of the Types,” ibid., par. 616.]

http://www.nyaap.org/jung-lexicon/i

Jung and the Four Psychological Functions

In Psychological Types Jung (1971/1921) describes four basic psychic functions that are capable of becoming conscious: intuition, sensation, feeling, and thinking:

Under sensation I include all perceptions by means of the sense organs; by thinking, I mean the function of intellectual cognition and the forming of logical conclusions; feeling is a function of subjective evaluation; intuition I take as perception by way of the unconscious, or perception of unconscious events. (p. 518)

Jung goes on to explain that, in his experience, there are only four basic functions, a fact that seems to be self-evident if one inquiries into the possibilities. These psychic functions are the methods employed by humans to acquire knowledge of themselves and the surrounding world; cognition is not restricted to one function, and each function provides its own kind of knowledge.

Of equal importance in Jung’s typology are the attitude types of introversion and extraversion, which he (1971/1921) describes as
distinguished by their attitude to the object. The introvert’s attitude is an abstracting one . . . he is always intent on withdrawing libido from the object, as though he had to prevent the object from gaining power over him. The extravert, on the contrary, has a positive relation to the object. He affirms its importance to such an extent that his subjective attitude is constantly related to and oriented by the object. (p. 330)

These brief explications of his major topics, namely, the eight variations of personality and the attitude types of introversion and extraversion, are later described as having this purpose:

To provide a critical psychology which will make a methodical investigation and presentation of the empirical material possible. First, and foremost, it is a critical tool for the research worker, who needs definite points of view and guidelines if he is to reduce the chaotic profusion of individual experiences to any kind of order. (1971/1921, p. 555)

Jung (1971/1921) said of his typology, “It is not a physiognomy and not an anthropological system, but a critical psychology dealing with the organization and delimitation of psychic processes that can be shown to be typical” (p. xv). Here Jung makes it clear that he was not concerned with the origins of the psychological functions, but used them as a tool in organizing empirical material. It was Jung’s purpose to describe individual types of the human personality, to explain and explore individual differences of cognition and various methods of expression in the personality by using the psychic functions of intuition, sensation, feeling, and thinking, along with the attitudinal types of introversion and extraversion.

Jung (1971/1921) states: “Since every man, as a relatively stable being possesses all the basic psychological functions, it would be a psychological necessity with a view to perfect adaptation that he should also employ them in equal measure” (p. 19). Here Jung confirms the possibility of all four functions working in equal measure in the psyche of one person. Throughout his writing, he describes what happens when one function is superior and conscious and another function is inferior and unconscious. When one conscious position is extreme, the position of the other extreme will exist in the unconscious, causing a neurosis or a maladaptation to consciousness.

The interplay of conscious and unconscious opposites, as well as opposites in general, is prevalent in Jung’s thinking and in his writing, and appears to be the foundation for his theory of opposites or the transcendent function. He (1971/1921) describes this as follows:

The “function” being here understood not as a basic function but as a complex function made up of other functions, and “transcendent” not as denoting a metaphysical quality but merely the fact that this function facilitates a transition from one state to another. The raw material shaped by thesis and antithesis, and in the shaping of which the opposites are united, is the living symbol. (p. 480)

This definition describes the importance that Jung gave to the symbol as a means for uniting the opposites, and also describes the complex relationship of the symbol with the four psychological functions.

An expanded individual consciousness was not seen as important only to the person who obtains the limits of personal potential, but equally important to the society to which he belongs. Jung (1953/1943) makes this clear when he says that “development of individuality is simultaneously a development of society. Suppression of individuality through the predominance of collective ideals and organizations is a moral defeat for society” (p. 303).

Fordham (1972) writes:

The subtitle of the first English translation of Psychological types reads or The psychology of individuation, an addition to the first Swiss edition and not added to later ones in German; it is omitted from the recent edition in the Collected works. The addition is curious because there is no mention of individuation in the text until its definition at the end of the book. (p. 112)

This is literally true, but not quite reflective of the spirit of the text, which I understand as significantly related to the individuation process. Meier (1986), however, appears to share my conviction concerning typology:

Jung’s most important contribution to psychology was the discovery and practice of the process of individuation. In spite of the supremacy of this concept, its origins in terms of chronology are far from being as clear as they should be, and in this respect not even Jung’s memoirs yield the needed biographical information.

But before I give you the prehistory, history and an account of the survival of the concept of individuation, I shall ask you to remember: Individuation begins and ends with typology. (emphasis Meier’s, p. 242)

I completely agree with Meier that individuation begins and ends with typology and that individuation was Jung’s most important contribution to psychology. I would describe Jung’s monumental work on psychological types as an attempt to take apart the human psyche and describe how the parts work. All of this work appears to revolve around the process of individuation, and the most important concept for achieving this end is the transcendent function, which is the symbol that unites the opposites.

Jung (1971/1921) describes and links his work on psychological functions with the concept of individuation in an important way:
The concept of individuation plays a large role in our psychology. In general, it is the process by which individual beings are formed and differentiated; in particular, it is the development of the psychological individual as a being distinct from the general, collective psychology. Individuation, therefore, is a process of differentiation having for its goal the development of the individual personality. (p. 448)

The above definition succinctly describes Jung’s purpose in attempting to provide a theoretical model of psychological types or functions. Individuation appears to me to be the primary goal of this work and Jung’s multitudinous insights are, as he described them, “critical tools” for further research.

Despite all the psychology we think we possess today, the psyche is still infinitely more obscure to us than the visible surface of the body. The psyche is still a foreign, almost unexplored country of which we have only indirect knowledge; it is mediated by conscious functions that are subject to almost endless possibilities of deception.
(Jung, 1933, pp. 74-75)

http://sulcus.berkeley.edu/flm/SH/MDL/GAL/GalDisChapts/galdis.chapter1.html