Judaism's historic openness to converts - a stance that helped it grow to encompass ten percent of the Roman Empire's population - stands in stark contrast to the defensive posture many Jewish communities maintain today. Through analysis of rabbinic literature, historical sources, and demographic data, this research traces how Jewish attitudes toward conversion evolved from biblical times through the contemporary American Jewish experience. The evidence reveals that positive attitudes toward converts (gerim) dominated rabbinic thought until medieval persecution forced Judaism to abandon active proselytizing. Now, as American Jewry faces a forty percent intermarriage rate and declining numbers, the "fortress mentality" that replaced Hillel's welcoming approach requires urgent reconsideration. Building on Reform Rabbi Alexander Schindler's outreach proposals, Conservative Judaism could develop comprehensive conversion programs including information centers, extended study periods, and public rituals of acceptance. Such proactive outreach to the "unchurched" would not merely represent innovation, but rather a return to Judaism's historical character - offering a constructive response to assimilation while enriching Jewish communities through the spiritual vitality that sincere converts bring to congregational life.