Final answer:
Paul championed the concept of universalism in opposition to the original Jewish Christians of Jerusalem, believing that the salvation offered by Christ was available to all people.
Step-by-step explanation:
After his conversion, Paul championed the important concept of universalism in opposition to the original Jewish Christians of Jerusalem. Paul popularized the idea that the salvation offered by Christ was potentially available to all people, not just Jews. This concept challenged the belief that membership in Christianity was limited to Jews and opened the faith to anyone who heard and embraced its teachings.