Let us now turn to the study of the Thinker and his vesture as they are found in men on earth. The body of the consciousness, conditioning it in the four lower subdivisions of the mental plane—the mental body, as we term it —is formed of combinations of the matter of these subdivisions. The Thinker, the individual, the Human Soul—formed in the way described in the latter part of this chapter— when he is coming into incarnation, first radiates forth some of his energy in vibrations that attract round him, and clothe him in, matter drawn from the four lower subdivisions of his own plane.
According to the nature of the vibrations are the kinds of matter they attract; the finer kinds answer the swifter vibrations and take form under their impulse; the coarser kinds similarly answer the slower ones; just as a wire will sympathetically sound out a note—a given number of vibrations—emitted by a wire similar in weight and tension to itself, but will remain dumb amid a chorus of notes from wires dissimilar to itself in these respects, so do the different kinds of matter assort themselves in answer to different kinds of vibrations. Exactly according to the vibrations sent out by the Thinker will be the nature of the mental body that he thus draws around him, and this mental body is what is called the lower mind, the lower manas, because it is the Thinker clothed in the matter of the lower subdivisions of the mental plane, and conditioned by it in his further working.
None of his energies which are too subtle to move this matter, too swift for its response, can express themselves through it; he is therefore limited by it, conditioned by it, restricted by it in his expression of himself. It is the first of his prison-houses during his incarnate life, and while his energies are acting within it he is largely shut off from his own higher world, for his attention is with the out-going energies and his life is thrown with them into the lower mind-body, often spoken of as a vesture, or sheath, or vehicle—any expression will serve which connotes the idea that the Thinker is not the mental body, but forms it and uses it in order to express as much of himself as he can in the lower mental region.
It must not be forgotten that his energies, still pulsing outwards, draw round him also the coarser matter of the astral plane as his astral body; and during his incarnate life, the energies that express themselves through the lower kinds of mental matter are so readily changed by it into the slower vibrations that are responded to by astral matter, that the two bodies are continually vibrating together, and become very closely interwoven; the coarser the kinds of matter built into the mental body, the more intimate becomes this union, so that the two bodies are sometimes classed together and even taken as one.
When we come to study Reincarnation we shall find this fact assuming vital importance. According to the stage of evolution reached by the man will be the type of mental body he forms on his way to become again incarnate, and we may study, as we did with the astral body, the respective mental bodies of three types of men—(a) an undeveloped man; (d) an average man; (c) a spiritually advanced man. (a) In the undeveloped man the mental body is but little perceptible, a small amount of unorganized mental matter, chiefly from the lowest subdivision of the plane, being all that represents it.
This is played on almost entirely from the lower bodies, being set vibrating feebly by the astral storms raised by the contacts with material objects through the sense-organs. Except when stimulated by these astral vibrations it remains almost quiescent, and even under their impulses its responses are sluggish.
No definite activity is generated from within, these blows from the outer world being necessary” to arouse any distinct response. The more violent the blows, the better for the progress of the man, for each responsive vibration aids in the embryonic development of the mental body. Riotous pleasure, anger, rage, pain, terror, all these passions, causing whirlwinds in the astral body, awaken faint vibrations in the mental, and gradually these vibrations, stirring into commencing activity the mental consciousness, cause it to add something of its own to the impressions made on it from without.
***From Annie Besant – The Ancient Wisdom