We tend to think of the consecutive developments of Greek philosophy, normative Judaism, and early Christianity as being exclusive to one another. But the opposite is in fact true: these schools shared many ideas, including how to understand and relate to the “Other,” the individual who lived outside of the community in question. Indeed, the very universalism that Christianity is credited with advancing was an extension of Jewish thought, which in turn was influenced by Stoicism.
As Greek schools, followed by schools within rabbinic Judaism and early Christianity, reached maturation, their boundaries became more rigid. But before this stage, in the Second Temple period, Judaism was a petri dish of ideas that nurtured a pluralism which invited all people to worship the Jewish God.
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]