334 THE AMERICAN JOURNAL OF SOCIOLOGY
The point of emphasis is that the desideratum of theoretical sociology is such familiarity with the mechanism of the social process that we shall have this abstract knowledge for practical use whenever it is called into requisition by the particular piece of work which we have in hand. The humor and the pathos in the characters of Don Quixote and Sancho Panza is precisely their innocence of this elementary insight into human conditions and proportions. There is both humor and pathos in some of the most ambitious sociological theories, as well as some of the most earnest social effort today, from like ignorance of relations that foreordain disappointment all along the line of unsophisti- cated effort.
These observations are equally applicable to each of the cate- gories in the present schedule and others that will follow. We return then to the particular category with which we are now concerned, namely, interdependence, although under the title "multiplicity" we have implied all that can be said in brief to emphasize the present detail.
It is one of the commonplaces of physical science that if a stone be thrown into a mill-pond, the waves produced will beat on the outer rim of space. Nobody professes that science has means of measuring the force of these waves beyond very restricted limits. But the motion once started affects all matter, although, for the most part, in an inappreciable degree. Simi- larly, the presence of each man in the world is a force that condi- tions the life of each other man. Each man diminishes the amount of available space in the world; he increases the demand for food ; he augments the potential supply of labor ; he multiplies the complexity of desires which must be coordinated if there is to be accommodated human action.
Within the economic realm this relation has been made familiar by an enormous body of literature and by the informal discussions of every interested group, whether of specialists or laymen. Beginning with the rudimentary facts of the division of labor, and enlarging the survey until it takes in theories of the reciprocal dependence of production, distribution, and con- sumption, economic doctrine has been the skirmish line of the
