It follows that the "Ego" embodied in this four-dimensional vehicle can no longer receive impressions through the three-dimensional sense organs and that it is wholly dependent for communication with the outside world on those which belong to the four-dimensional vehicle. The nature of the impressions received will depend on the degree of development of these organs. If they are completely undeveloped the Ego will be utterly oblivious of its surroundings, whereas if they are well developed the reverse will be the case and we may suppose the Ego to be as fully cognizant of the surrounding world as we are in ordinary waking life. It is interesting to compare with this the statements of those who claim to have consciously explored the "Astral plane" or four space world. They often describe sleepers as being present, but "in a brown study." Compare also the statement often found in communications purporting to emanate from discarnate personalities to the effect that, "We have seen so-and-so, but do not know whether he is dead or not." Of course, it by no means follows that it will be possible, even under these latter conditions, to remember in waking life the impressions received during unconsciousness. On the contrary we should expect this to be the exception rather than the rule. In their passage from sense organ to consciousness the impressions received will, _ex hypothesi_, not pass through the physical brain and the memory centres with which they become associated may be located in a position which is inaccessible to consciousness when embodied in the physical vehicle. It would be possible, though not perhaps absolutely necessary, to account on these lines for the impression which most people have sometimes had, of apparently "remembering" a place which they have certainly never visited previously in waking life. They might, however, on this theory, have done so in sleep. It would also account for those dreams in which the dreamer perceives an incident at a distance which is subsequently verified. As for the ordinary chaotic dream, this, it seems to me may be accounted for in either of two main ways. If we suppose that the stimulation of certain cells (memory centres) in the brain causes an uprush into consciousness of the associated item of memory or "souvenir," it is not unreasonable to suppose that such stimulation is going on _in the body_ all the time. But it will only be in the state, intermediate between profound sleep and waking, that these aroused souvenirs will, on the one hand get through to the consciousness--which in deep sleep is separated from the body altogether--and, on the other will escape over-ruling by the Will or obliteration by the influx of normal sensory impressions. This would account for the fact that the majority of dreams appear to be of very short duration and to take place in the very act of waking.