Normal consciousness is that which functions during waking hours, when the brain is in full physiological activity, freely and completely related to the outer physical world. This consciousness is more or less developed according to the individual, but its component parts--sensation, emotion, sentiment, reason, intelligence, will, intuition--do not exceed known limits; for instance, we do not find clairvoyance, the prophetic faculty, and certain other abnormal faculties, which we shall class under the higher consciousness. The higher consciousness works in the astral body, whether externalised or not; it seldom manifests itself, and then incompletely; it is accompanied by the more or less complete inhibition of the senses, and by a kind of sleep in which the relations of the subject with the physical world are wholly or partially suspended. The characteristics of this state are greater keenness of the normal faculties, and the appearance of new ones, which are often inexplicable and extraordinary and the more remarkable in proportion as sleep is more profound, the brain calmer, or the physiological state more abnormal. How can we explain the paradox that faculties shown by a brain in a state of inactivity cover an extent of ground which the brain in a state of activity cannot approach? The reason is that the brain, in this case, is not an instrument moved directly by the cause of consciousness, _the soul_, but a simple recipient, which the soul, then centred in the astral body, impresses _on returning to the physical body_ (if it has been far away) or impresses directly when, whilst acting in the finer vehicle, the latter has not left the body.[4] In other words, the brain, by reason of its functional inactivity, vibrates little or not at all in its higher centres; it plays the part of a sounding-board at rest, capable of vibrating sympathetically under the influence of a similar board placed by its side. The necessity of cerebral quiet, if the higher consciousness is to make an impression, is now easy to understand; the finer vibration of the astral body cannot be impressed upon the brain when the latter is already strongly vibrating under the action of normal consciousness. For this reason also, the deeper the sleep of the physical body the better the higher consciousness manifests itself. In ordinary man, organic quiet is scarcely ever complete during sleep; the brain, as we shall see shortly, automatically repeats the vibrations which normal consciousness has called forth during the waking state; this, together with an habitual density of the nervous elements, too great to respond to the higher vibration, explains the rarity and the confused state of the impression of astral consciousness on the brain. The facts relating to the higher consciousness are as numerous as they are varied. We shall not enter into full details, but choose only a few phenomena quoted in well-known works.