Our words and other modes of expression are but the description of the flow of images in our minds, and our problem is to make a similar stream flow through the mind of the listener; but strange indeed would it be to make others see a situation which we ourselves cannot see; strange if we could draw a picture without being able to follow its outlines as we draw. Or suppose we are teaching science, and our object is to explain the composition of matter to someone, and make him understand how light, heat, etc., depend on the theory of matter; strange if the listener should get a picture if we ourselves are unable to get it. Or, once more, suppose we are to describe some incident, and our aim is to make its every detail stand out so clearly that no one can miss a single one. Is it not evident that we can never make any of these images more clear to those who listen to us or read our words than they are to ourselves?
2. THE MATERIAL USED BY IMAGINATION
What is the material, the mental content, out of which imagination builds its structures?
Images the Stuff of Imagination.—Nothing can enter the imagination the elements of which have not been in our past experience and then been conserved in the form of images. The Indians never dreamed of a heaven whose streets are paved with gold, and in whose center stands a great white throne. Their experience had given them no knowledge of these things; and so, perforce, they must build their heaven out of the images which they had at command, namely, those connected with the chase and the forest. So their heaven was the "happy hunting ground," inhabited by game and enemies over whom the blessed forever triumphed. Likewise the valiant soldiers whose deadly arrows and keen-edged swords and battle-axes won on the bloody field of Hastings, did not picture a far-off day when the opposing lines should kill each other with mighty engines hurling death from behind parapets a dozen miles away. Firearms and the explosive powder were yet unknown, hence there were no images out of which to build such a picture.
I do not mean that your imagination cannot construct an object which has never before been in your experience as a whole, for the work of the imagination is to do precisely this thing. It takes the various images at its disposal and builds them into wholes which may never have existed before, and which may exist now only as a creation of the mind. And yet we have put into this new product not a single element which was not familiar to us in the form of an image of one kind or another. It is the form which is new; the material is old. This is exemplified every time an inventor takes the two fundamental parts of a machine, the lever and the inclined plane, and puts them together in relations new to each other and so evolves a machine whose complexity fairly bewilders us. And with other lines of thinking, as in mechanics, inventive power consists in being able to see the old in new relations, and so constantly build new constructions out of old material. It is this power which gives us the daring and original thinker, the Newton whose falling apple suggested to him the planets falling toward the sun in their orbits; the Darwin who out of the thigh bone of an animal was able to construct in his imagination the whole animal and the environment in which it must have lived, and so add another page to the earth's history.
The Two Factors in Imagination.—From the simple facts which we have just been considering, the conclusion is plain that our power of imagination depends on two factors; namely, (1) the materials available in the form of usable images capable of recall, and (2) our constructive ability, or the power to group these images into new wholes, the process being guided by some purpose or end. Without this last provision, the products of our imagination are daydreams with their "castles in Spain," which may be pleasing and proper enough on occasions, but which as an habitual mode of thought are extremely dangerous.
Imagination Limited by Stock of Images.—That the mind is limited in its imagination by its stock of images may be seen from a simple illustration: Suppose that you own a building made of brick, but that you find the old one no longer adequate for your needs, and so purpose to build a new one; and suppose, further, that you have no material for your new building except that contained in the old structure. It is evident that you will be limited in constructing your new building by the material which was in the old. You may be able to build the new structure in any one of a multitude of different forms or styles of architecture, so far as the material at hand will lend itself to that style of building, and providing, further, that you are able to make the plans. But you will always be limited finally by the character and amount of material obtainable from the old structure. So with the mind. The old building is your past experience, and the separate bricks are the images out of which you must build your new structure through the imagination. Here, as before, nothing can enter which was not already on hand. Nothing goes into the new structure so far as its constructive material is concerned except images, and there is nowhere to get images but from the results of our past experience.
Limited Also by Our Constructive Ability.—But not only is our imaginative output limited by the amount of material in the way of images which we have at our command, but also and perhaps not less by our constructive ability. Many persons might own the old pile of bricks fully adequate for the new structure, and then fail to get the new because they were unable to construct it. So, many who have had a rich and varied experience in many lines are yet unable to muster their images of these experiences in such a way that new products are obtainable from them. These have the heavy, draft-horse kind of intellect which goes plodding on, very possibly doing good service in its own circumscribed range, but destined after all to service in the narrow field with its low, drooping horizon. They are never able to take a dash at a two-minute clip among equally swift competitors, or even swing at a good round pace along the pleasant highways of an experience lying beyond the confines of the narrow here and now. These are the minds which cannot discover relations; which cannot think. Minds of this type can never be architects of their own fate, or even builders, but must content themselves to be hod carriers.
The Need of a Purpose.—Nor are we to forget that we cannot intelligently erect our building until we know the purpose for which it is to be used. No matter how much building material we may have on hand, nor how skillful an architect we may be, unless our plans are guided by some definite aim, we shall be likely to end with a structure that is fanciful and useless. Likewise with our thought structure. Unless our imagination is guided by some aim or purpose, we are in danger of drifting into mere daydreams which not only are useless in furnishing ideals for the guidance of our lives, but often become positively harmful when grown into a habit. The habit of daydreaming is hard to break, and, continuing, holds our thought in thrall and makes it unwilling to deal with the plain, homely things of everyday life. Who has not had the experience of an hour or a day spent in a fairyland of dreams, and awakened at the end to find himself rather dissatisfied with the prosaic round of duties which confronted him! I do not mean to say that we should never dream; but I know of no more pernicious mental habit than that of daydreaming carried to excess, for it ends in our following every will-o'-the-wisp of fancy, and places us at the mercy of every chance suggestion.