The difference between the effect of a thought-wave and that of a thought-form is that the thought-wave, does not produce a definite complete idea, but tends to produce a thought as the same character as itself; a thought-wave is thus much less definite in its action, but reaches a far wider circle. A thought-form on the other hand, does convey a definite complete idea, transferring the exact nature of the thought to those prepared to receive it, but it can reach only one person at a time.
Thus a thought-wave is eminently adaptable; a wave of devotion, for example, would tend to arouse devotion in the recipient, although the object of the devotion might be quite different in the case of the sender and the receiver. But a thought-form would give rise to a precise image of the being for whom the devotion was originally felt.
If the thought is sufficiently strong, distance makes absolutely no difference to the thought-form, but the thought of an ordinary person is usually weak and diffused, and is, therefore, not effective outside a limited area.
A thought-form, say of love or of desire to protect, directed strongly towards another person, goes to the person thought of, and remains in his aura as a shielding and protecting agent; it will seek all opportunities to serve, and all opportunities to defend, not by a conscious and deliberate action but by a blind following out of impulse impressed upon it, and it will strengthen friendly forces that impinge on the aura and weaken unfriendly ones. Thus are created and maintained veritable guardian angels round those we love. Many a mother’s “prayer” for a distant child thus circles round him, acting in the manner described.
A knowledge of these facts should make us conscious of the enormous power placed in our hands. We may repeat here what was said when we were dealing with thought-waves, viz., that there are many cases where we may not be able to do anything for a man on the physical plane. The man’s mental [and astral] bodies, however, can be affected, and they are frequently more easily impressible than his physical body. Hence it is always open to us to affect his mental or astral body by helpful thought, affectionate feeling etc. The laws of thought being what they are, it is certain that results must accrue; there is no possibility of failure, even though no obvious consequence may follow on the physical plane.
***From Arthur E. Powell – The Mental Body