An analysis of the primitive forms of laughter, which precede its regulation by a reference to ideas, has disclosed the fact that it is the expression of pleasure, yet not of all pleasure, but only of the sudden oncoming or increase of pleasure, of what we call gladness. It has shown us, further, that this joy of laughter is, in many, if not in all cases, conditioned by a sudden relaxation of mental strain, and may, indeed, be described by reference to this condition as a sense of relief from pressure. This was seen to hold good alike in those graver situations in which nervous laughter is apt to occur, in the lighter ones, such as the escape of schoolboys from the classroom to the playground, and in the still lighter ones in which the strain relaxed is momentary only, of which the laughter induced by tickling is the best representative. Now it seems evident that we have in all these experiences something analogous to play. The natural alliance of laughter with the play-mood has already been touched on.[83] We may now go a step farther and say that these spurts of joyous consciousness which, in simple natures untrammelled by thought of appearances, express themselves in laughter are of the essence of Play. To be glad with the gaiety of laughter, to throw off the stiff and wearing attitude of seriousness and to abandon oneself to mirth and jollity is, in truth, to begin to play. The deep kinship between laughter and play discloses itself as soon as we begin carefully to compare them. Let us look at some of their common characteristics. Play contrasts with work, not as rest or inactivity contrasts with it, but as light pleasurable activity contrasts {146} with the more strenuous and partly disagreeable kind. The same holds good of laughter. It is light pleasurable activity in contrast to the more burdensome activity of our serious hours. Again, play is free activity entered upon for its own sake. That is to say, it is not directed to any end outside itself, to the satisfaction of any want, save that of the play-impulse itself; and so it is free from external restraint, and from the sense of compulsion—of a “must” at the ear, whether embodied in the voice of a master or in that of a higher self—which accompanies the attitude of the worker. Similarly, when we laugh we are released from the strain and pressure of serious concentration, from the compulsion of the practical and other needs which keep men, in the main, serious beings. It follows at once that play is relative to work, that it is enjoyed as a relief from graver occupations, and cannot be indefinitely prolonged. And, as has been hinted above, the same holds true of laughter and what we appropriately describe as playing the fool.