Contrary to the common contention that the Catholic Church triumphed in Counter-Reformation Poland, this study reveals that from the rise of the Reformation and the rapid dissemination of its new ideas, the Catholic Church was overcome with a strong sense of insecurity. The beleaguered Church sought to separate Catholics from non-Catholics: Jews and heretics. This process helped form a Polish identity that led to racial anti-Semitism and to the exclusion of even most assimilated Jews from the category of Poles. The book portrays Jews not only as victims of Church persecution but as active influential participants in Polish society.