This essay focuses on the work of a Jewish scholar of Christianity, Joseph Klausner, who did his work at the beginning of the twentieth century. More broadly, it examines what I consider to be the symbiotic relationship between New Testament scholarship, or, more precisely, scholarship about Second Temple and Rabbinic Judaism and early Christianity, and Jewish-Christian relations. Beginning with the Enlightenment, many scholars and theologians, both Jewish and Christian, have analyzed Christian attitudes toward Jews and Judaism. Jewish attitudes to Christianity, though by no means totally ignored, have received less attention. One explanation for this imbalance is the now widely shared view that the historical realities of the relationship between Jews and Christians have been tragic. This realization has resulted in the desire on the part of both Jews and Christians to study and explain the past and, for some, also to draw moral, religious, social, and political lessons from it.