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 next in size, by a wide margin, are the two British WUPJ-affiliates. In 2010, the Movement for Reform Judaism and Liberal Judaism respectively had 16,125 and 7,197 member households in 45 and 39 communities, or 19.4% and 8.7% of British Jews registered at a synagogue. Other member organizations are based in forty countries around the world. They include the Union progressiver Juden in Deutschland, which had some 4,500 members in 2010 and incorporates 25 congregations, one in Austria; the Nederlands Verbond voor Progressief Jodendom, with 3,500 affiliates in 10 communities; the 13 Liberal synagogues in France; the Israel Movement for Reform and Progressive Judaism (5,000 members in 2000, 35 communities); the Movement for Progressive Judaism (Движение прогрессивного Иудаизма) in the CIS and Baltic States, with 61 affiliates in Russia, Ukraine and Belarus and several thousands of regular constituents; and many other, smaller ones.