When a man uses his mental body, i.e.,, when he thinks, a vibration is set up in the mental body, and this vibration produces two distinct results. The first result is that of radiating vibrations or waves; these we shall deal with in the present chapter, reserving the second result -the production of thought-forms for a later chapter.
A vibration in the mental body, like all other vibrations, tends to communicate itself to any surrounding matter which is capable of receiving it precisely as the vibration of a bell communicates itself to the surrounding air. Hence, since the atmosphere is filled with mental matter, which responds very readily to such impulses, there is produced a sort of ripple, a kind of vibrating shell, formed in the matter of the plane, which spreads out through circumambient space exactly as the dropping of a stone into a pond produces ripples which radiate from the centre of impact over the surface of the water in every direction. In the case of a mental impulse the radiation is not in one plane only but in many dimensions, more like the radiations from the sun or from a lamp.
The rays thrown out cross in all directions without interfering with one another in the slightest degree, just as do rays of light on the physical plane. Moreover, the expanding sphere of vibrations is many-coloured and opalescent, but its colours grow fainter as it spreads away. As already said, the mental vibration also tends to reproduce itself wherever opportunity is offered to it. Consequently, whenever the thought-wave strikes upon another mental body it will tend to set up in it vibrations similar to those which gave it birth in the first instance. That is to say, when a man’s mental body is struck by a thought-wave there arises a tendency in his mind to produce a thought similar to that which had previously arisen in the mind of the originator of the wave.
The thought-wave becomes less powerful in proportion to the distance from its source, though it is probable that the variation is proportional to the cube of the distance instead of to the square, because of the additional dimension involved. Nevertheless, these mental vibrations lose their power very much more gradually than those in physical matter and seem to be exhausted, or at least to become so faint as to be imperceptible, only at an enormous distance from their source.
There is, of course, an infinite variety of thoughts; if the thought is perfectly simple there will be in the mental body only the one rate of vibration, and consequently only one type of mental matter will be strongly affected. The mental body, as we have seen, consists of matter of the four lower sub-planes of the mental plane, and in each of these sub-planes there are many sub-divisions of varying densities. If a man is already deeply engrossed in some other line of thought, a strong wave of thought may sweep past him without affecting him, precisely as a man already occupied in business or pleasure may not hear the voice of another speaker.
As, however, large numbers of men do not think definitely or strongly except when in immediate prosecution of some business which demands their whole attention, they are likely at other times to be considerably affected by the thoughts which impinge upon them. Hence great responsibility rests upon everyone who thinks, because his thoughts, especially if strong and clear, will inevitably affect large numbers of other people.
***From Arthur E. Powell – The Mental Body