IMAGINATION AND THINKING.--We have already considered the use of imagination in interpreting the thoughts, feelings and handiwork of others. Let us now look a little more closely into the part it plays in our own thinking. Suppose that, instead of reading a poem, we are writing one; instead of listening to a description of a battle, we are describing it; instead of looking at the picture, we are painting it. Then our object is to make others who may read our language, or listen to our words, or view our handiwork, construct the mental images of the situation which furnished the material for our thought. 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.