Not long ago, everyone knew that Judaism came before Christianity. More recently, scholars have begun to recognize that the historical picture is quite a bit more complicated than that. In the Jewish world of the first century, many sects competed for the name of the true Israel and the true interpreter of the Torah the Talmud itself speaks of seventy and the form of Judaism that was to be the seedbed of what eventually became the Christian Church was but one of these many sects. Scholars have come to realize that we can and need to speak of a twin birth of Christianity and Judaism, not a genealogy in which one is parent to the other. In this book, the author develops a revised understanding of the interactions between nascent Christianity and nascent Judaism in late antiquity, interpreting the two new religions as intensely and complexly intertwined throughout this period. Although the officials of the eventual winners in both communities the Rabbis in Judaism and the orthodox leaders in Christianity sought to deny it, until the end of late antiquity many people remained both Christians and Jews. This resulted, among other things, in much shared religious innovation that affected the respective orthodoxies as well.