The Mental Highway
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The first of the psychological elements is cognition — the power to know, which we may think of as a series of sensations. These sensations are so complex that we can never be sure of a final possible analysis. Their apparent simplicity is really the result of previous combinations below the threshold of consciousness. For instance, the pleasantness of food depends on the delicate skin of the palate and is largely a matter of touch. Smell and sight also play a part, so that taste is a very complex sensation. Analysis of the sensations of hearing and sight reveal the same truth as to their complex nature.

Some mental elements are simpler than those distinctly received through the sensations. So that consciousness is the sum of sensations whose units themselves are not absolutely simple, but have arisen by a synthesis of still simpler elements.

As we consider the relative independence of sensation, we observe a far greater elasticity in some sense organs than others. Touch can distinguish a thousand distinct sensations per minute. We can distinguish thirty-five to forty electric shocks in the same length of time. Sight stands lowest in this respect. A swinging torch loses its identity in a circle of fire. Rapid visual images prevent the optic nerve from adjusting.

So, for a sensation to arise, the sensation must stand out from some background. An interval of time and a contrast between the present and the preceding sensation must exist. If we experience a strong electric shock, we will not notice a weaker one. We do not feel two pains in the same region. Producing temporary sensation in a given region suspends the previous sensation.

In a highly excited state of consciousness, even strong impressions get little hold. The ecstasy of hysteria does also.

The threshold of consciousness is not always at the same level. Contrast with preceding or simultaneous sensations raise it, and custom or accommodation lowers it. As in watching a bird’s flight into the distance, we can discern it long after we look for it for the first time or can possibly see it. That which appears as pleasure today may report as pain tomorrow, and vice versa.

The law of relativity is that a sensation’s relation to other sensations determines the existence and properties of it. Sensation arises from within and from without, as the sensation of effort and muscular sensation such as tension, fatigue and cramp. In all special sensations the movements of the organism play an important part, as in taste in connection with the movements of the tongue. The delicacy of touch in different parts of the body stands in definite relation to the mobility of those parts, being greater in the tongue, lips, and fingers, and least in the chest and back.

Sensation is influenced not only by preceding and simultaneous sensations, but by the idea of a sensation. Conscious life would be impossible without the repetitions of idea sensations. Not that we can exactly recall the sensation, however, we at once fuse the idea with the given sensation, and so it does not stand as a free and independent representation. We involuntarily classify it, and reference the sensation to previous ones of like kind.

In studying the mechanism of thought, sensation and perception appear to be associated with different brain centers. Sensation is possible in an animal deprived of the cerebrum, while perception can take place only when the cerebrum is intact. These centers are always connected. In cases of great mental shock from grief or of long continued mental strain, we see a functional disturbance called dissociation of ideas. The patient loses the power to combine sensations with corresponding reproductions, and in extreme cases produces a condition of dual personality in which the subject sees his friends and surroundings but fails to recognize them as such.

We may lose the power to understand written or spoken words, although the sight and hearing are unimpaired. The path from the concept to the word is open, but the path from the word to the concept is closed. We see the same difficulty occasionally in some diseases as in the after effects of paralysis in which the patient speaks an utterly different word from that which he intended or that which fits the occasion.

Not only can we recall and recognize single sensations, but whole groups of them, causing a complex perception, and most of our perceptions are complex. Thus consciousness has at its disposal a content that makes it independent of the influences of the moment. One may pass a life in memory, a life of thought, not merely a life of sensation and perception. One may perpetuate a state of pleasant melancholia indefinitely without reference to the present realities. We cannot, of course, completely isolate ourselves from the world.

There are two streams in consciousness, one being determined by the sensation present then, the ideas it tends to excite, and the other composed of a series of free ideas which previous sensation has aroused. Between these there is an inverse ratio. They try to suppress each another. They battle for the attention, sensation first having the upper hand, then representation. One moment we are under the control of sensation, reflection and deep thought bury us in the next.

There are three possible fields of conscious living. One is to give up wholly to the play of sensations (musical and artistic natures). Another is to value sensations only as they may be recognized and classified (observers and naturalists). The third is to live mainly in the realm of free ideas, in memory, imagination, and abstract thought.

The distinction between the free flow of ideas and the actual percepts of consciousness is that we come to recognize one as possibility and the other as reality. The distinction is possible because we have the power of becoming conscious that the elements produced were experienced in time past. Every state of consciousness has two poles.

Through one it is associated with preceding, through the other with succeeding elements of consciousness. Memory provides the connection with the past, but hope with the future. Life struggles forever forward and is moved to look backward only by experiencing check.

We gather the unity of conscious life from these facts about cognition. While we may never be fully conscious of ourselves, we may know that we know, what we know, and ourselves as knowing beings. Self is the sum of all consciousness. This synthesis of consciousness is always relative and struggling. If the contrasts in the content of consciousness are too great, the mold breaks.

The disquiet at puberty and the menopause are difficult to formulate into the unity of consciousness, but if we can hold them until they are fully incorporated into the content of conscious unity, we can probably recognize that the transition is continuous and consequent. The failure to synthesize any new or strange element in the content of consciousness marks the beginning of the dissolution of conscious unity.

The process begins with a disturbance of the vital feeling, which the patient cannot understand. The effects of existence are new and interrupted. The fundamental experiences do not repeat themselves. He begins to doubt his own existence and that of others. The things that happen to him are distant and shadowy. He becomes estranged from himself. He refers his experiences to another. Sometimes memory connection is lost and he is in a stage of double consciousness. Two states succeed each other and he appears a different person in each. When he reaches the stage where the different states and periods are lacking in common elements, the conscious life is in dissolution.

An illusion is an inaccurate perception, while an hallucination is an imaginary perception, or a perception without an object. Illusions of any of the senses may occur in normal people, while hallucinations are usually indicative of abnormal conditions. Goethe was able to produce hallucinations at will. When the subject recognizes the hallucination as such there is no serious reaction. For a complete understanding of these phases of consciousness see any standard work on psychiatry, or abnormal psychology.