Even when awake we are ignorant what impulses set up trains of thought. We know not why this or that idea “comes into the head.” The suggesting cause is often so slight as to be imperceptible. The brain is an organ of inconceivable sensitiveness. Its fibres are so delicate that millions are packed into the circumference of a sixpence. Yet has each fibre its own function and each is a musical chord competent to catch and to vibrate to motions of the ether which the senses cannot perceive. It is probable (not proved) that in sleep, when not distracted by the claims of the nerve system and the thronging impressions brought by the senses; these brain fibres are vastly more sensitive and moved by still slighter action of the ether than in waking life. In Dream we never lose the consciousness of our own identity. We retain our individuality. You dream often that you are _something_ other than you are, but never that you are some other _person_. Does not this indicate the existence of an entity, other than the dreaming brain, which preserves its oneness and its sanity while the material organ with which it is associated and through which it communicates with the external world is, as it were, forgetting its reason, its experience and itself, and so becoming in very truth insane. And here we touch upon the most perplexing characteristic of dream. We are conscious of existence, of individuality, and, in a slight degree, of sense impressions. We have ideas, reflections, emotions, sentiments, passions. We can invent stories, construct characters, endow them with dramatic language, paint ideal pictures, make speeches, compose music and conduct a train of argument. But withal we are not rational. We can _think_ wise things, but we _are_ the veriest fools of nature. Every mental faculty is awake and alive—save one—namely, the faculty, whatever it be, that enables us to distinguish between fancy and fact, between the possible and the impossible, the congruous and the incongruous; the faculty, in brief, which separates sanity from insanity. In dream, with rare exceptions, we are not conscious that we are dreaming. Fancies are accepted as facts, shadows as substances, the ideal as the real. And they are so accepted without suspicion or doubt. We _see_ them, _hear_ them, _feel_ them. Nothing in our actual waking life is more real to us than are the unrealities of dream at the moment of dreaming. Probably there are few readers who have not occasionally dreamed that they were dreaming, and while noting the drama have said to themselves “this is a dream.” But these are rare exceptions to the rule that a dream is accepted by the sleeping mind as an event of actual occurrence and the scenes and persons implicitly believed to be objective and not subjective; that is to say—as being then actually existing in the external world.