So we come to distinguish grades of consciousness. The lower limit, or zero grade, is unconsciousness. This condition, which consists in an absolute absence of all psychical interconnections, is essentially different from the disappearance of single psychical contents from consciousness. The latter is continually taking place in the flow of mental processes. Complex ideas and feelings and even single elements of these compounds may disappear, and new ones take their places. This continuous appearance and disappearance of elementary and composite processes in consciousness is what makes up its successive interconnection.
Without this change, such an interconnection would, of course, be impossible.
Any psychical element that has disappeared from consciousness, is to be [p. 208] called unconscious in the sense that we assume the possibility of its renewal, that in its reappearance in the actual interconnection of psychical processes. Our knowledge of an element that has become unconscious does not extend beyond this possibility of its renewal. For psychology, therefore, it has no meaning except as a disposition for the rise of future components of psychical processes which are connected with others before present. Assumptions as to the state of the "unconscious" or as to "unconscious processes" of any kind which are thought of as existing along with the conscious processes of experience, are entirely unproductive for psychology. There are, of course, physical concomitants of the psychical dispositions mentioned, of which some can be directly demonstrated, some inferred from various experiences. These physical concomitants are the effects which practice produces on all organs, especially those of the nervous system. As a universal result of practice we observe a facilitation of action which renders a repetition of the process easier. To be sure, we do not know any details in regard to the changes that are effected in the structure of the nervous elements through practice, but we can represent them to ourselves through very natural analogies with mechanical processes, such, for example, as the reduction of friction resulting from the rubbing of two surfaces against each other.
It was noted in the case of temporal ideas, that the member of a series of successive ideas which is immediately, present in our perception, has the most favorable position. Similarly in the simultaneous interconnection of consciousness, for example in a compound clang or in a series of new objects, certain single components are favored above the others. In both cases we designate the differences in perception as differences in cleanness and distinctness. Clearness, is the, relatively favorable comprehension of the object in itself [p. 209] distinctness the sharp discrimination from other objects, which is generally connected with clearness. The state which accompanies the clear grasp of any psychical. content and is characterized by a special feeling, we call attention. The process through which any such content is brought to clear comprehension we call apperception. In contrast with this, perception which is not accompanied by a state of attention, we designate apprehension. Those contents of consciousness upon which the attention is concentrated are spoken of, after the analogy of the external optical fixation point, as the fixation-point of consciousness, or the inner fixation-point. On the other hand, the whole content of consciousness at any given moment is called the field of conscious. When a psychical process passes into an unconscious state we speak of its sinking below the threshold of consciousness and when such a process arises we say it appears above the threshold of consciousness. These are all figurative expressions and must not be understood literally. They are useful, however, because of the brevity and clearness they permit in the description of conscious processes.
5. If we try to describe the train of psychical compounds in their interconnection with the aid of these figurative expressions, we may say that it is made up of a continual coming and going. At first some compound comes into the field of consciousness and then advances into the inner fixation-point, from which it returns to the field of consciousness before disappearing entirely. Besides this train of psychical compounds which are apperceived, there is also a coming and going of others which are merely apprehended, that is, enter the field of consciousness and pass out again without reaching the inner fixation-point. Both the apperceived and the apprehended compounds may have different grades of clearness. In the case of the first class this appears in [p. 210] the fact that the clearness and distinctness of apperception in general is variable according to the state of consciousness. To illustrate: it can easily be shown that when one and the same impression is apperceived several times in succession if the other conditions remain the same, the successive apperceptions are usually clearer and more distinct. The, different degrees of clearness in the case of compounds that, merely apprehended, may be observed most easily when the impressions are composite. It is then found, especially when the impressions last but an instant, that even here,: where all the components are obscure from the first, that there are still different gradations.
Some seem to rise more above the threshold of consciousness, some less.
6. These relations can not be determined through chance introspections, but only by systematic experimental observations.
The best kinds of conscious contents to use for such observations are ideas because they can be easily produced at any time through external impressions.