It is only by a complete psychological description, however, even a physiological explanation, that we can hope to fathom the tremendous significance of rhythm in music and poetry. Those treatments which expose its development in the dance and song really beg the question; they assume the very fact for which we have to find the ground, namely, the natural impulse to rhythm. Even those theories which explain it as a helpful social phenomenon, as regulating work, etc., fail to account for its peculiar psychological character--that compelling, intimate force, the "Zwang" of which Nietszche speaks, which we all feel, and which makes it helpful. This compelling quality of rhythm would lead us to look behind the sociological influences, for the explanation in some fundamental condition of consciousness, some "demand" of the organism. For this reason we must find superficial the views which connect rhythm with the symmetry of the body as making rhythmical gesture necessary; or more particularly with the conditions of work, which, if it is skilled and well carried out, proceeds in equal recurring periods, like the swinging of a hammer or an axe. But it appears that primitive effort is not carried on in this way, and proceeds, not from regularity to rhythm, but rather, through, by means of rhythm, which is made a help, to regularity. Again, it is said that work can be well carried out by a large number of people, only in unison, only by simultaneous action, and that rhythm is a condition of this. The work in the cotton fields, the work of sailors, etc. requires something to give notice of the moment for beginning action. Rhythm would then have arisen as a social function. Against this it may be said that signals of this kind might assist common action without recurring at regular intervals, while periodicity is the fundamental quality of rhythm. Thus this theory would explain a natural tendency by its effect.