How comes this transformation from sanity to insanity, wrought in a moment, when Sleep has closed upon the Mind the portals of the senses and left it almost isolated from the real material external world to revel in its own imaginary world? Some rein that held the mind in check when awake has certainly been taken from it at the instant sleep occurs. What is that lost rein—that paralyzed power? It is not _Consciousness_. We do not lose our individuality in dream. Never does the dreamer suppose himself to be another person. He may dream that he has assumed other characters, that he is a king, or a beggar, but still it is _himself_ who has become a king and is _acting_ king. Nor is _the Will_ absent. The dreaming mind is conscious of the exercise of its Will and believes that its commands are obeyed. But the Will is powerless to compel action. Its commands are _not_ obeyed. In dream we _will_ to speak, to run, to do what the body does freely when in our waking state we _will_ to do. We _will_ in dream as we _will_ when awake, but the mechanism of the nerves that move the body refuses to obey the mandate of the Will however strenuously exerted. _Imagination_, on the other hand, is even more lively in dream than in our waking time. The _Reasoning Faculties_ are not asleep, for we _argue_, often rightly—only we reason upon wrong premisses. We accept the visions of the mind—the ideas presented to the Conscious Self—as being real and then we reason upon them rationally. What Lawyer has not often dreamed that he was addressing a logical legal argument to an approving Court and, when wakened, remembering and reviewing that argument, has found it to be without a flaw? The _Emotions_ are not extinguished when we dream. The presentation of imaginary incidents which, if they had been real, would have kindled the passions in waking life, rouse those self-same passions to equal if not to greater fury in dream. Nor is the _passion_ fanciful. We do not merely dream that we are angry. Very real and hot anger is kindled by the fancy-born picture of the dream, as the reader will readily discover if he recalls the sensation that attends upon being awakened at the moment of irritation in a dream. It is with all the other passions and emotions as with anger. The incidents of a dream excite them as if those incidents were true. Wherefore? Because they appear to the mind to be true. Thus by a process of exhaustion we may hope to arrive at some knowledge of the cause of the special characteristic of dream—that is to say, the _absolute belief we have in its reality during its enactment_. The inquiry cannot fail to throw a great light upon mental structure and upon the relationship of the mind to the body and to the external world.