THAT political struggles are based upon economic interests is to-day disputed by few students of society. The attempt has been made in this work to trace the various interests that have arisen and struggled in each social stage and to determine the influence exercised by these contending interests in the creation of social institutions.

      Back of every political party there has always stood a group or class which expected to profit by the activity and the success of that party. When any party has attained to power, it has been because it has tried to establish institutions or to modify existing ones in accord with its interests.

      Changes in the industrial basis of society - inventions, new processes, and combinations and methods of producing and distributing goods -- create new interests with new social classes to represent them. These improvements in the technique of production are the dynamic element that brings about what we call progress in society.

      In this work I have sought to begin at the origin of each line of social progress. I have first endeavored to describe the steps in mechanical progress, then the social classes brought into prominence by the mechanical changes, then the struggle by which these new classes sought to gain social power, and, finally, the institutions

which were created or the alterations made in existing institutions as a consequence of the struggle, or as a result of the victory of a new class. It has seemed to me that these underlying social forces are of more importance than the individuals that were forced to the front in the process of these struggles, or even than the laws that were established to record the results of the conflict. In short, I have tried to describe the dynamics of history rather than to record the accomplished facts, to answer the question, "Why did it happen?" as well as, "What happened?"

      An inquiry into causes is manifestly a greater task than the recording of accomplished facts. It is certain that I have made some mistakes, probably a great many, in analyzing the underlying forces of so complex a thing as American social development. The finding of such mistakes will prove nothing as to the method save that the leisure of ten very busy years in the life of one individual is all too short a time in which to trace to their origin the multitude of forces that have been operating in American history.

      This work has been the more difficult since only a few, historians, and these only in recent years, have given any attention to this viewpoint. It was, therefore, necessary for me to spend much time in the study of "original documents,"- the newspapers, magazines, and pamphlet literature of each period. In these, rather than in the "musty documents" of state, do we find history in the making. Here we can see the clash of contending interests before they are crystallized into laws and institutions.

      I have not sought after new or bizarre facts. I have

sought rather to understand the reasons for those whose existence is undisputed. Occasionally I have found things which seemed to be neglected in the familiar histories and have stated these. In my references, also, I have tried to name the most accessible works rather than to multiply references and strain after scholastic effect with many citations of seldom used and almost inaccessible material.

      In this connection it should be stated that most of this work was written before the publication of the "Documentary History of American Society," edited by Dr. R. T. Ely and John R. Commons of the University of Wisconsin. Otherwise I should have made more frequent reference to its pages. Thanks to the courtesy of these editors, however, I had an opportunity to consult their notes and the original publications upon which that work is based, and this service is here gratefully acknowledged.