It comes, then, to this: that to be “viable,” livable, or merely practical, life must be lived as a game—and the “must” here expresses a condition, not a commandment. It must be lived in the spirit of play rather than work, and the conflicts which it involves must be carried on in the realization that no species, or party to a game, can survive without its natural antagonists, its beloved enemies, its indispensable opponents.