In the foreword to his book on “The Reformation in Germany,” Prof. Henry C. Vedder makes this statement: “The great religious struggle of the sixteenth century was only a phase of the social revolution then going on in Europe and effecting a transformation of all its institutions. Momentous economic changes were the underlying cause of political and religious movements.… The external events of the Reformation have been told before with substantial accuracy; what is now needed is illumination of the facts by the light of this new knowledge.” The present study on the Reformation in Poland attempts to gather together material of social and economic nature and to point out that the underlying causes of the rise and spread of the Reformation in Poland were chiefly social and economic rather than religious, or even purely political. Viewed in this light, the rapid rise and the phenomenal growth of the Polish Reformation, as well as its almost complete collapse in the course of the following century, become quite intelligible. Had the movement had its roots in deep religious convictions, it would have survived the changes in social institutions, but, having been inspired and stimulated in its early development by economic motives, it lost its dynamic force with changed economic conditions by the end of the sixteenth century. Owing to the fact that the writer has had access to only a part of the great abundance of source material bearing on this subject, the study does not pretend to be exhaustive. However, it has the merit of being the first attempt to portray the development of the Polish Reformation in the light of economic causes, and in the judgment of the writer the conclusions here reached and the interpretation given the movement are essentially sound. In this place the writer wishes to express his indebtedness to Dr. John M. Vincent, Professor of European History at Johns Hopkins University, for his encouragement in the prosecution of this study and for his valuable suggestions and criticisms, and to Miss Mary C. Stokes, of the Historical Department in the University, for her careful reading of the manuscript before its going to press. THE REFORMATION IN POLAND SOME SOCIAL AND ECONOMIC ASPECTS CHAPTER I DEVELOPMENT OF THE REFORMATION IN POLAND _The Background of the Polish Reformation._--The Reformation found in Poland a fertile soil and a congenial atmosphere for its spread and growth.