ABSTRACT
The development of intelligence follows, therefore, instead of the easier line of habit, a line of greater resistance; but from the very reason that it demands a stronger manifestation of the will to live it has become productive of the greatest gains of evolution. And yet, although the development of intelligence has enabled man to master his environment and to make it serve the needs of a life as far beyond the animal's as that is from the life of a plant, the advance has not been unmixed gain. In the human stage of psychological evolution, play has also another purpose—that of recreation; and in this form has a considerable value in adult life as well as in youth. Most animals do not require recreation of this sort, for their energies are fully occupied by instinctive activities of various kinds, and they find their needed recreation in rest.
