Universalism has nothing to do with welcoming converts into one’s faith community, which actually runs counter to universalism. The concept of conversion depends on a particularist “in” or “out” framework in which all of humankind falls into two categories. Either one falls within a particular faith community, in which he or she reaps the benefits of being a member of God’s elect people, or outside the faith community, or one is defined according to what he or she is not: he is not elect, he is not chosen, and he is not, according to most opinions, going to be saved in the end of days.
As opposed to Judaism, Christianity has been credited as being a universalist faith. It was Paul, many say, who was responsible for arguing that all people could enter into the covenantal community through faith in Jesus, rather than through “works,” that is, the observance of Mosaic law. Yet the idea that all one has to do to become part of a faith-community is to believe in Jesus is still a particularist viewpoint. This idea relies on an “in” and “out” model of humanity. The foundational core of universalism must lie outside the realm of conversion.
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]