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.
Historical background of the New Testament
Historians seek to understand where Jesus and his followers fit among other Jewish factions at the time. According to the Jewish-Roman historian Flavius Josephus, the three parties in contemporary Judaism were the Pharisees, the Sadducees and the Essenes, the last of these three being apparently marginalized and in some cases retired to quasi-monastic communities. Josephus also speaks of a "Fourth Movement", "Zealots", "Lestai" or "Sicarii".
The Pharisees were a powerful force in 1st-century Judea. Early Christians shared several beliefs of the Pharisees, such as resurrection, retribution in the next world, angels, human freedom, and Divine Providence. After the fall of the Temple, the Pharisaic outlook was established in Rabbinic Judaism. Some scholars speculate that Jesus was himself a Pharisee. In Jesus' day, the two main schools of thought among the Pharisees were the House of Hillel, which had been founded by the eminent Tanna, Hillel the Elder, and the House of Shammai. Jesus' assertion of hypocrisy may have been directed against the stricter members of the House of Shammai, although he agreed with their teachings on divorce. Jesus also commented on the House of Hillel's teachings (Babylonian Talmud, Shabbat 31a) concerning the greatest commandment and the Golden Rule. Historians do not know whether there were Pharisees in Galilee during Jesus' life, or what they would have been like.