It will generally be allowed that the distinctive feature of play as opposed to work is that of spontaneity. The action itself is of no consequence, one man's play is another man's work. Nor does it seem to matter whence comes the feeling of compulsion in work, whether from pressure of outer necessity, or from an inner necessity like the compelling force of duty. Where there is joy in creation or in discovery the work and play of the genius approach the standpoint of the child, Indulging every instinct of the soul, There, where law, life, joy, impulse are one thing. In the play of early childhood there may be freedom, not only from adult authority, but even from the restrictions of nature or of circumstances since "let's pretend" annihilates time and space and all material considerations. Among theories of play first comes what is known as the Schiller-Spencer theory, in which play is attributed to the accumulation of surplus energy. When the human being has more energy than he requires in order to supply the bodily needs of himself and his family, then he feels impelled to use it. As the activities of his daily life are the only ones known to him, he fights his battles over again, he simulates the serious business of life, and transfers, for instance, the incidents of the chase into a dance. In this Way he reaches artistic creation, so that "play is the first poetry of the human being." As an opposite of this we get a Re-creation theory, where play, if not too strenuous, understood as a change of occupation, rests and re-creates. Another theory is that of recapitulation, which has been emphasised by Stanley Hall, according to which children play hunting and chasing games, or find a fascination in making tents, because they are passing through that stage of development in which their primitive ancestors lived by hunting or dwelt in tents. Lastly, a most interesting theory is that which is associated with the name of Groos, and which is best expressed in the sentence: "Animals do not play because they are young, but they have their youth because they must play," play being regarded as the preparation for future life activities. The kitten therefore practises chasing a cork, the puppy worries boots and gloves, the kid practises jumping, and so on.