Origins of Judaism
For centuries, the traditional understanding has been that Judaism came before Christianity and that Christianity separated from Judaism some time after the destruction of the Second Temple in 70 CE. Starting in the latter half of the 20th century, some scholars have begun to argue that the historical picture is quite a bit more complicated than that. In the 1st century, many Jewish sects existed in competition with each other, see Second Temple Judaism. The sects which eventually became Rabbinic Judaism and Early Christianity were but two of these. Some scholars have begun to propose a model which envisions a twin birth of Christianity and Judaism rather than a separation of the former from the latter. For example, Robert Goldenberg (2002) asserts that it is increasingly accepted among scholars that "at the end of the 1st century CE there were not yet two separate religions called "Judaism" and "Christianity"".
Daniel Boyarin (2002) proposes a revised understanding of the interactions between nascent Christianity and nascent Rabbinical Judaism in Late Antiquity which views the two religions as intensely and complexly intertwined throughout this period.
Reform Judaism
The various regional branches sharing these beliefs, including the American Union for Reform Judaism (URJ), the Movement for Reform Judaism (MRJ) and Liberal Judaism in Britain, and the Israel Movement for Reform and Progressive Judaism, are all united within the international World Union for Progressive Judaism. Founded in 1926, the WUPJ estimates it represents at least 1.8 million people in 50 countries: close to a million registered adult congregants as well as numerous unaffiliated individuals who identify with it.