http://www.literoscope.org/en/jung-psychological-types/122-feeling/ said:
20. Feeling (Fühlen): I count feeling among the four basic psychological functions. I am unable to support the psychological school that regards feeling as a secondary phenomenon dependent upon presentations or sensations, but in company with Höffding, Wundt, Lehmann, Külpe, Baldwin, and others, I regard it as an independent function sui generis.
Feeling is primarily a process that takes place between the ego and a given content, a process, moreover, that imparts to the content a definite value in the sense of acceptance or rejection ('like' or 'dislike'); but it can also appear, as it were, isolated in the form of 'mood', quite apart from the momentary contents of consciousness or momentary sensations. This latter process may be causally related to previous conscious contents, though not necessarily so, since, as psychopathology abundantly proves, it can take origin equally well from unconscious contents. But even the mood, whether it be regarded as a general or only a partial feeling, signifies a valuation; not, however, a valuation of one definite, individual, conscious content, but of the whole conscious situation at the moment, and, once again, with special reference to the question of acceptance or rejection.
Feeling, therefore, is an entirely subjective process, which may be in every respect independent of external stimuli, although chiming in with every sensation. Even an 'indifferent' sensation possesses a 'feeling tone', namely, that of indifference, which again expresses a certain valuation. Hence feeling is also a kind of judging, differing, however, from an intellectual judgment, in that it does not aim at establishing an intellectual connection but is solely concerned with the setting up of a subjective criterion of acceptance or rejection. The valuation by feeling extends to every content of consciousness, of whatever kind it may be. When the intensity of feeling is increased an affect (v. Affect) results, which is a state of feeling accompanied by appreciable bodily innervations. Feeling is distinguished from affect by the fact that it gives rise to no perceptible physical innervations, i.e. just as much or as little as the ordinary thinking process.
Ordinary 'simple' feeling is concrete (q.v.), i.e. it is mixed up with other function-elements, frequently with sensation for instance. In this particular case we might term it affective, or (as in this book, for instance) feeling-sensation, by which a well-nigh inseparable blending of feeling with sensation elements is to be understood. This characteristic fusion is universally present where feeling is still an undifferentiated function, hence most evidently in the psyche of a neurotic with a differentiated thinking.
Although feeling is an independent function in itself, it may lapse into a state of dependence upon another function, upon thinking, for instance; whereby a feeling is produced which is merely kept as an accompaniment to thinking, and is not repressed from consciousness only in so far as it fits in with the intellectual associations.
It is important to distinguish abstract feeling from ordinary concrete feeling. For, just as the abstract concept (v. Thinking) does away with the differences of the things embraced in it, so abstract feeling, by being raised above the differences of the individual feeling-values, establishes a 'mood', or state of feeling, which embraces and therewith abolishes the different individual values. Thus, just as thinking marshals the conscious contents under concepts, feeling arranges them according to their value. The more concrete the feeling, the more subjective and personal the value it confers; but the more abstract it is, the more general and objective is the value it bestows. Just as a completely abstract concept no longer coincides with the individuality and peculiarity of things, only revealing their universality and indistinctness, so too the completely abstract feeling no longer coincides with the individual instant and its feeling quality but only with the totality of all instants and their indistinctness. Accordingly, feeling like thinking is a rational function, since, as is shown by experience, values in general are bestowed according to the laws of reason, just as concepts in general are framed after the laws of reason.
Naturally the essence of feeling is not characterized by the foregoing definitions: they only serve to convey its external manifestations. The conceptual capacity of the intellect proves incapable of formulating the real nature of feeling in abstract terms, since thinking belongs to a category quite incommensurable with feeling. In fact, no basic psychological function whatsoever can be completely expressed by any other one. This circumstance is responsible for the fact that no intellectual definition will ever be able to render the specific character of feeling in any adequate measure. The mere fact that feelings are classified adds nothing to the understanding of their nature, because even the most exact classification will be able to yield only that intellectually seizable content to which or with which feelings appear connected, but without thereby apprehending the specific nature of feeling. Thus, however many varying and intellectually seizable classes of contents there may be, just as many feelings can be differentiated, without ever arriving at an exhaustive classification of feelings themselves; because, beyond every possible class of contents accessible to the intellect, there still exist feelings which are beyond intellectual classification. The very idea of a classification is intellectual and therefore incommensurable with the nature of feeling. Hence, we must content ourselves with our attempts to define the limits of the concept.
The nature of a feeling-valuation may be compared with intellectual apperception as an apperception of value. An active and a passive feeling-apperception can be distinguished. The passive feeling-act is characterized by the fact that a content excites or attracts the feeling; it compels a feeling-participation on the part of the subject* The active feeling-act, on the contrary, confers value from the subject it is a deliberate evaluation of contents in accordance with feeling and not in accordance with intellectual intention. Hence active feeling is a directed function, an act of will, as for instance loving as opposed to being in love. This latter state would be undirected, passive feeling, as, indeed, the ordinary colloquial term suggests, since it describes the former as activity and the latter as a condition. Undirected feeling is feeling-intuition. Thus, in the stricter sense, only the active, directed feeling should be termed rational: the passive is definitely irrational, since it establishes values without voluntary participation, occasionally even against the subject s intention.
When the total attitude of the individual is orientated by the function of feeling, we speak of a feeling-type.
(Fi), which is cognizant of the constant, non-changing aspects of society (allowing the Fi user to actively indulge these aspects or rebel against them), and is generally referenced any time social etiquette, common courtesy, or good manners is mentioned. 
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