This book explores the diverse views of Gentile impurity found in Second Temple and rabbinic sources. Christine Hayes seeks to to determine the role such views played in the rise and development of sectarianism within late antique society and in the regulation of Jewish - Gentile interactions. In ancient Jewish culture the ideas of purity served to define the socio - cultural boundaries between Jews and Gentile others. A proper understanding of Jewish notions of Gentile impurity is therefore crutial to an accurate reconstruction of Jewish atitudes towards, and interaction with non-Jews. Hayes discovers that different views on the question of Gentile impurity led to widely varying definitions of group identity and the permeability of group boundaries among the ancient Jews. These differing views of impurity resulted in widely divergent atitudes towards intermarriage and conversion-The two processes by which boundaries may be penetrated.The crucial difference, Hayes finds, is the extent to which impurity is seen as racial and inherited rather than determined by religious and moral practice.She argues that different views of the possibility of conversion , based on differing ideas about impurity, were the key factor in the formation of Jewish sects in the second temple period, and in the seperation of the early Christian Church from what would later be rabbinic Judaism.