WHAT is hypnosis? We cannot go far astray if we define it as a condition outwardly resembling sleep and characterized by extreme credulousness.

We have already studied concentration in its relation to normal states of mind, and have learned that the effect upon consciousness of a suggested belief depends upon the degree of concentration of the consciousness to which it is presented. In other words, that the extent of the influence of a proffered suggestion depends upon the degree of equilibrium, as to impulses and inhibitions, of the consciousness to which the suggestion is addressed.

Now, no new principle is involved in hypnotism. The most startling effects of hypnotic suggestion are not due to any special power flowing from mind to mind, but to a change of equilibrium of the subject's own mind.

All that is needed to prepare the soil for the accomplishment of this change is the induction of a degree of credu-lousness greater than the normal. The mind in a state of abnormal credulous-ness will accept and believe any ideas that are proffered to it, even ideas that are contradicted by the plain testimony of the senses.

Let us experiment. By a few minutes' talk, coupled with the voluntary composure of the subject, we bring him into a deep hypnotic trance. He is now unable to resist any suggestion we may make that does not positively violate his standards of morality. Whether the suggestion is one arousing an impulse to inhibit an action, as "You will not lift your foot," or one instilling a belief that necessarily inhibits an action, as "You cannot lift your foot," the effect is the same; the foot is glued to the floor. If we tell him that his friend has left the room, he will neither see that friend nor hear any word that the friend may utter, and a hat placed on the friend's head will seem to hang in mid-air. Every sense-impression not in accord with our suggestions is inhibited and shifted into subconsciousness without having been consciously perceived. The process is the same as that during sleep, when for the mother all sound impressions are inhibited except those from her restless child.

What has happened to our subject? Were the empty words we uttered sufficient in themselves, like a mystic formula, to bring about the change?

By no means. I might have produced the same effect by a few monotonous passes with the hands, or by requiring the subject to gaze at my finger held close before his eyes. It is possible for me to have hypnotized him automatically, as it were, my thoughts being actually otherwise engaged. I might have used one of the various devices of revolving mirrors to focus his attention, thus eliminating my own personality as a factor in the process. I might even in some cases have merely sent him a letter advising him that two minutes after reading it he would fall into the hypnotic sleep; and under certain conditions the phenomenon would have occurred, even though in the mean time I had been removed by death from the possibility of exerting a personal influence.

Obviously, then, hypnotism is not necessarily the result of any special energy, like magnetism, or even of an exercise of the operator's will. No special qualifications are required. Almost any intelligent person can hypnotize or be hypnotized.

How is so strange a mental transformation to be accounted for?

We might compare it to sleep. But can that be sleep in which the mind is unusually quick in its associative imagery and in which the causal judgments are faultlessly correct? If I tell our subject that he is standing in a canon of the Colorado Rockies, he sees glaciers and snowy mountains, tumbling waterfalls and rocky gorges. These things are pictured, not in the distorted form of dreams, but vividly, truthfully. His mind is awake; but thoughts and impulses in conflict with my suggestion are inhibited.

To be sure, the easiest method of inducing hypnosis is to suggest to the subject the belief that he is falling asleep. This is because such a belief tends to inhibit all ideas, all consciousness, leaving the mind a blank page to receive the suggestions of the operator.

But natural sleep is marked by a comparative torpidity of the senses and a diminution of discriminatory power, while hypnosis is characterized by an increased sensitiveness and a quickened memory in the field suggested by the operator.

In this field sense-impressions are perceived that would pass unnoticed by the normal consciousness, and memories long forgotten and inaccessible are brought forth.

Besides all this, the profound or somnambulic state of hypnosis shades off into countless transitional or so-called "hypnoidal" states in which the readiness to believe remains, but in which the resemblances to sleep are scarcely discernible.

For the explanation of hypnosis we must refer to the process of attention.

We have elsewhere observed that inhibition is an essential element of every act of attention. Everything not related to the subject attended to is inhibited, while a great number of sense-impressions, ideas and complexes that are so related can be simultaneously active in consciousness. The inhibition rests only on those complexes requiring a contrary mental attitude.

The hypnotic state is marked by an abnormal increase in selective and inhibitory power. The sense organs of the hypnotic, just as in a normal state, positively shout aloud the fact that his friend is standing before him, but they are powerless before a discriminating attention so controlled that it may allow his consciousness to perceive nothing but the friend's hat.

In fact, hypnosis is nothing more nor less than a state of "over-attention." Attention under normal circumstances means only special distinctness of the object attended to; "over-attention" in hypnosis means unquestioning faith in all that comes from the object attended to - that is to say, the operator.

Eye, the monotonous speech, the thoughts of sleep, the tired feeling all withdraw attention from all othei things and fasten it upon the one absorbing idea of the hypnotizer. All that the hypnotizer says and does is seized upon with avidity, and absorbed with blind acceptance. The subject is told that he cannot speak, and the motor impulses necessary to speech are inhibited. What can he do but surrender helplessly to life as a mute? The sug-gestional influence operates automatically.

Hypnosis, then, is a state of "over-attention," or, in the phrase we have adopted, a state of mental concentration.

And the results of mental concentration when thus exhibited overwhelm us with wonder unless we are careful to remember the infinite complexity of the mental apparatus.

If we lose sight of this complexity and wide-reaching power of the mind, we are apt to feel, in considering hypnotism, as if one person had exerted a mysterious influence over the other, as if the will of one had in some uncanny fashion mastered the will of the other.

As soon, however, as we realize that physical health and functional disturbance, belief and action, judgment and conduct, happiness and despair, are all the result of the co-operation of a vast number of mental forces, which have had to overcome and inhibit conflicting mental forces, when we realize that every one of these results is the outcome of an overbalancing of this complex mechanism, then we understand how it is possible for deliberately directed influences from without or from within to help one side or the other to preponderance.

With these explanations and illustrations of the powers and practical uses of an abnormal degree of mental concentration, and how this condition can be deliberately brought about by devices that lull the mind into a condition of receptivity, as it is employed by eminent psychologists and psychotherapists under the name of "hypnotism," the student must be well fortified in the essential principles of mental control.

He is now fitted to appreciate, understand and make use of practical instructions. Succeeding books will therefore be devoted to methods and directions for the attainment of success by scientific psychological practices.