[Footnote 11: An up-to-date riddle asks the difference between the quick and the dead, and answers, "The quick are those who get out of the way of a motor-bus and the dead are those who do not."] Froebel recognised many kinds of play. He realised that much of the play of boyhood is exercise of physical power, and that it must be of a competitive nature because the boy wants to measure his power. Even in 1826 he urges the importance not only of town playgrounds but of play leaders, that the play may be full of life. Among games for boys he noted some still involving sense-play, as hiding games, colour games and shooting at a mark, which need quick hearing and sight, intellectual plays exercising thought and judgement, _e.g._ draughts and dramatic games. One form of play which seemed to him most important was constructive play, where there is expression of ideas as well as expression of power. This side of play covers a great deal, and will be dealt with later; its importance in Froebel's eyes lies in the fact that through construction, however simple, the child gains knowledge of his own power and learns "to master himself." Froebel wanted particularly to deepen this feeling of power, and says that the little one who has already made some experiments takes pleasure in the use of sand and clay, "impelled by the previously acquired sense of power he seeks to master the material." In order to gain real knowledge of himself, of his power, a child needs to compare his power with that of others. This is one reason for the child's ready imitation of all he sees done by others. Another reason for this is that only through real experience or action can a child gain the ideas which he will express later, therefore he must reproduce all he sees or hears. "In the family the child sees parents and others at work, producing, doing something; consequently he, at this stage, would like to represent what he sees. Be cautious, parents. You can at one blow destroy, at least for a long time, the impulse to activity and to formation if you repel their help as childish, useless or even as a hindrance.... Strengthen and develop this instinct; give to your child the highest he now needs, let him add his power to your work, that he may gain the consciousness of his power and also learn to appreciate its limitations." As the child's sense of power and his self-consciousness deepen he requires possessions of his "very own." Says Froebel: "The feeling of his own power implies and demands also the possession of his own space and his own material belonging exclusively to him. Be his realm, his province, a corner of the house or courtyard, be it the space of a box or of a closet, be it a grotto, a hut or a garden, the boy at this age needs an external point, chosen and prepared by himself, to which he refers all his activity."