When the purgatorial life is at an end and the astral body disintegrates in its turn, the soul functions in the mental body, in the mental world.[241] On this new plane, the memory of the worlds left behind continues, though far less clearly than the memory of the physical existed in the astral world; this is owing to the fact that, in ordinary man, the mental body is not sufficiently developed to constitute a complete vehicle of consciousness, capable of registering all the vibrations that come to it; everything in the past that has been purely the work of the astral or the physical plane then disappears from his memory; there remain only memories that have been caused either by the mental qualities or qualities superior to these, all the highest elements concerned with affection, intelligence, or art. The mental world, generally speaking, is seen only to a small extent or not at all, because of the incomplete development of the mental body. Besides, recollections assume a new character[242]; every thought takes a concrete form—that of a friend, for instance, appears as the friend himself, speaking and thinking, more vivid than on the earth plane[243]; everything is dramatised in marvellous fashion, and life is intense throughout the realms of paradise.
The mental body, after exhausting the forces that make it up, also dies, and the soul is "centred" in the only vehicle it has left, the causal body, a body that is immortal, one may say, up to a certain point, since the soul retains it until the time comes when it can function in a still higher and more lasting vehicle,[244] and this happens only after millions of years.[245] Here, another diminution of memory takes place, because the soul loses a large portion of its consciousness when it comes into contact with none but the vibrations of this body, which is even more incompletely developed than the former ones, though holding within itself all the germs of these latter. The Ego then remains apparently sunk in sleep for a varying period, though never for very long; then the germs in the causal body become active, build up a new series of bodies in succession—the mental, the astral, and finally the physical—and the soul returns once more to incarnation.
It will now be understood how it comes about that a soul of average development—on entering a new cycle, with the memory of the last cycle considerably obliterated by the loss of the physical, astral, and mental bodies, sheathed in new bodies on these planes, bodies that have nothing in common with the life of the past—is unable to impress its dim memories on to the brain; but it will also be seen that, with the progress of evolution, the soul acquires ever clearer consciousness in the causal body, in which it finally preserves the memory of the various life-cycles. Since, at this stage, it has become capable of projecting its vibrations, voluntarily, through the lower bodies, it is able to transmit this memory first to the mental body, then to the astral, and lastly to the physical body; when this is possible, man, in waking consciousness, remembers his former lives.
This transmission requires a purificatory process in the vehicles and a special training of the will. The matter of all the bodies—that of the brain in particular—must be refined, its constituent elements must be subtler, and its atoms must be fully awakened to activity[246]; whereupon the cerebral cell becomes capable of responding to the thought of the Ego, i.e., of vibrating in harmony with the higher matter.
The second condition of the brain's receptivity is that this organ be brought into a state of complete rest. So long as the waking consciousness is active, the brain vibrates powerfully, and if, at this time, the soul sends the brain its thought, this latter can no more make an impression on the existing cerebral activity than a faint note could be heard amid the clash of an orchestra. Consequently, man, by the training of his will, must have acquired the power to stop the thinking activity in the waking state, and to "centre" his attention on the causal body, the only vehicle in which he can know the facts of his past incarnations; this done he is able, at will, to project on to his brain the scenes of his former lives and to imprint them thereon with greater distinctness, in proportion to his development and training.
In order to avoid continued explanations, we will deal with another side of the question, however incomprehensible it be to such as have not studied theosophy.
A vehicle of consciousness is both a registering apparatus[247] and a conductor of vibrations.[248] The kinds of matter of which forms are made up are perfectly graduated; the finest atom of the physical body is built up of the densest atoms of the astral plane, the finest atom of the astral body is made of the densest atoms of the mental plane, and so on. Each atom is linked to the one that precedes and to the one that follows it in that immense chain which stretches from the densest to the subtlest plane of the Cosmos. Every vibration follows this path, passes in all directions—in the seven[249] dimensions of space-and terminates in the very Centre of consciousness, the Logos, God incarnate in the world.
It is then comprehensible, even logical, that God should be both conscious, on his receptive side, of everything that takes place in the world (omniscient), and should produce, on his active side, all the forces of the world (omnipotent). It is likewise admissible that the human soul, when fully developed, should find in the causal body the memory of the facts that have echoed therein, from the time when it could function consciously in it. But, it will be asked, how could it find, in the causal body, memories of existences it has not been able to register individually, of which it has not been conscious, those, for instance, that form the early stages of its evolution at a time when it was conscious only in the lower vehicles?
Memory possesses many store-houses. The vibrations of which it is composed affect the whole Universe, there is not a single local shock that is not felt throughout all the worlds. The eternal registering of things takes place in the great centre of consciousness, God, or rather, it exists in him, for to him there is neither future nor past, only one eternal present; evolution is unceasingly accomplished[250]; but if we look upon ourselves as finite beings, living in the illusion of time and space, we find that vibrating matter preserves for a longer or a shorter period the movement imparted to it. The denser the substance, which forms the medium in which vibration takes place, the feebler the vibration; that is why it speedily ceases on the physical plane; it continues long, however, in the higher conditions of matter, and it is there we must look for it,[251] if we would recall certain events at which we have not been present. When anything exciting, a murder, a battle, for instance, has happened anywhere, the subtler atoms of the surrounding objects receive a powerful shock and continue to vibrate for centuries. Those who have developed their inner senses can thus witness the scene which is continually repeating itself, or rather, is happening all the time.[252] Thus, psychometrists,[253] in presence of a portion of a fossil, are enabled to bring back scenes that this fragment has witnessed millions of years ago.[254]