The mind should be supplied with the proper material for the exercise of this faculty. As Halleck says: "Since the imagination has not the miraculous power necessary to create something out of nothing, the first essential thing is to get the proper perceptional material in proper quantity. If a child has enough blocks, he can build a castle or a palace. Give him but three blocks, and his power of combination is painfully limited. Some persons wonder why their imaginative power is no greater, when they have only a few accurate ideas." It thus follows that the active use of the Perceptive faculties will result in storing away a quantity of material, which, when represented or reproduced by the Memory, will give to the Constructive Imagination the material it requires with which to build. The greater the general knowledge of the person, the greater will be his store of material for this use. This knowledge need not necessarily be acquired at first hand from personal observation, but may also be in the nature of information acquired from the experience of others and known through their conversation, writings, etc. The necessity of forming clear concepts is very apparent when we come to exercise the Constructive Imaginative. Unless we have clear-cut ideas of the various things concerned with the subject before us, we cannot focus the imagination clearly upon its task. The general ideas should be clearly understood and the classification should be intelligent. Particular things should be clearly seen in "the mind's eye;" that is, the power of visualization or forming mental images should be cultivated in this connection. One may improve this particular faculty by either writing a description of scenes or particular things we have seen, or else by verbally describing them to others. As Halleck says: "An attempt at a clear-cut oral description of something to another person will often impress ourselves and him with the fact that our mental images are hazy, and that the first step toward better description consists in improving them."