Shaye J. D. Cohen in the context of "Split of early Christianity and Judaism"

Christianity began as a movement within Second Temple Judaism, but the two religions gradually diverged over the first few centuries of the Christian Era, and the Christian movement perceived itself as distinct from the Jews by the fourth century. Historians continue to debate the dating of Christianity's emergence as a discrete religion apart from Judaism. Philip S. Alexander characterizes the question of when Christianity and Judaism parted company and went their separate ways (often termed the parting of the ways) as "one of those deceptively simple questions which should be approached with great care". According to historian Shaye J. D. Cohen, "the separation of Christianity from Judaism was a process, not an event", in which the church became "more and more gentile, and less and less Jewish". Conversely, various historical events have been proposed as definitive points of separation, including the Council of Jerusalem and the First Council of Nicaea.

Historiography of the split is complicated by a number of factors, including the diverse and syncretic range of religious thought and practice within Early Christianity and early Rabbinic Judaism (both of which were far less orthodox and theologically homogeneous in the first centuries of the Christian Era than they are today) and the coexistence of and interaction between Judaism, Jewish Christianity, and Gentile Christianity over a period of centuries at the beginning of Early Christianity. Scholars have found evidence of continuous interactions between Jewish-Christian and Rabbinic movements from the mid-to late second century CE to the fourth century CE. The first centuries of belief in Jesus have been described by historians as characterized by religious creativity and "chaos".