Abstract ideas usually represent themselves by all kinds of perfect and most beautiful geometrical forms. It should be remembered in this connection that the merest abstractions to us down here become definite facts, on the mental plane. The strength of thought and emotion determines the size of the thought-form as well as its duration as a separate entity. Its duration depends upon the nutriment supplied to it after its generation by the repetition of the thought either by its originator or by others.
If the thought be intellectual and impersonal -eg. If the thinker is attempting to solve a problem in algebra or geometry -then his thought-forms [as well as his thought waves] will be confined to the mental plane. If his thought is of a spiritual nature, eg., if it be tinged with love and aspiration of deep, unselfish feeling, then it will rise upwards from the mental plane and will borrow much of the splendour and glory of the buddhic levels above. In such a case its influence is most powerful and every such thought is a mighty force for good. If, on the other hand, the thought has in it something of self or personal desire, at once its vibrations turn downwards, and it draws round itself a body of astral matter in addition to its clothing of mental matter. Such a thought-form -which would be termed more accurately a thought – emotion -form -is, of course, capable of affecting both the mental and the astral bodies of other men.
This type of thought-form is by far the most common, as few thoughts of ordinary men and women are untinged with desire, passion, or emotion. We may consider this class of thought-forms as generated by the activity of kama-manas, i.e.,, by mind dominated by desire. When a man thinks of any concrete object -a book, a house, a landscape -he builds a tiny image of the object in the matter of his mental body. This image floats in the upper part of that body, usually in front of the face of the man and at about the level of the eye. It remains there as long as the man is contemplating the object, and usually for a little time afterwards, the length of time depending upon the intensity and the clearness of thought. This form is quite objective and can be seen by another person possessed of mental clairvoyance.
If a man thinks of another person he creates a tiny portrait in just the same way. The same result follows any effort of the “imagination”. The painter who forms a conception of his future picture builds it up out of the matter of his mental body, and then projects it into space in front of him, keeps it before his mind’s eye, and copies it. The novelist, in the same way, builds images of his characters in mental matter, and by the exercise of his will moves these puppets from one position or grouping to another, so that the plot of the story is literally acted out before him.
As already said, these mental images are so entirely objective that they may not only be seen by a clairvoyant, but they can even be moved about and re-arranged by some one other than their creator. Thus for example, playful nature spirits or more often a “dead” novelist, watching the work of his fellow-author, will move the images or puppets about so that they seem to their creator to have developed a will of their own, the plot of the story thus working out on lines quite different from those originally intended by the author. A sculptor makes a strong thought-form of the statue he intends to create, plants it in his block of marble, and then proceeds to cut away the marble which lies outside the thought-form until only that portion of it which it interpenetrated by the thought-form remains.
Similarly, a lecturer, as he thinks earnestly of the different parts of his subject, makes a series of thought-forms, usually strong ones, because of the effort. If he fails to make his audience understand him it must be largely because his own thought is not sufficiently clear cut. A clumsy and indefinite thought-form makes but a slight impression, and even that with difficulty, whilst a clearly-cut one forces the mental bodies of the audience to try to reproduce it. Hypnotism provides examples of the objectivity of thought-forms.
***From Arthur E. Powell – The Mental Body