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.
Jewish atheism
There has been a phenomenon of atheistic and secular Jewish organizations, mostly in the past century, from the Jewish socialist Bund in early twentieth-century Poland to the modern Congress of Secular Jewish Organizations and the Society for Humanistic Judaism in the United States. Many Jewish atheists feel comfortable within any of the three major non-Orthodox Jewish denominations (Reform, Conservative, and Reconstructionist). This presents less of a contradiction than might first seem apparent, given Judaism's emphasis on practice over belief, with even mainstream guides to Judaism suggesting that belief in God is not a necessary prerequisite to Jewish observance. However, Orthodox Judaism regards the acceptance of the "Yoke of Heaven" (the sovereignty of the God of Israel in the world and the divine origin of the Torah) as a fundamental obligation for Jews. Even among non-Orthodox Jews, espousing atheism remains problematic outside of the Congress of Secular Jewish Organizations and the Society for Humanistic Judaism. The Reform movement, for example, has rejected efforts at affiliation by atheistic temples. The presence of atheists in all denominations of modern Judaism, from Secular Humanistic Judaism to Orthodoxy, has been noted.