Many Jews in the Second Temple period believed that Israel shares a special relationship with God, and at the same time, that all people are capable of participating in a covenantal relationship with God. But as boundaries between religious communities began to lose their fluidity in the early centuries of the Common Era, Jewish universalism became untenable outside of a legal framework. While many Christians embraced the idea that all of humanity can participate in the same covenantal community through a common faith in Christ, the rabbis based their brand of Judaism not on world-wide accessibility, but on a commitment to a common legal system which encompassed ethical values. What makes the Second Temple period so unique is that much of its literature sees no need for hard distinctions between religious communities. At the same time, it was this period during which the most fundamental aspects of what would become rabbinic Judaism took form.
Dr. Malka Z. Simkovich, “The Origins of Jewish Universalism: What it is, and Why it Matters”, Lehrhaus (6 October 2016) [http://www.thelehrhaus.com/scholarship/jewish-universalism]