According to Pulver Family Assistant Professor of Jewish Studies David Freidenreich, a priest, a minister and a rabbi would not have walked into a bar together in pre-modern times. If, by some chance, they had ended up in the same eating facility, they would be at different tables, eating different food that was prepared in different ways.

Freidenreich introduced his book, Foreigners and Their Food: Constructing Otherness in Jewish, Christian, and Islamic Law, at the “Food and Identity in Judaism, Christianity and Islam” event on Wednesday, Nov. 30. The book describes the influence that religion has had on how people with different beliefs interact, cohabitate and eat with one another, noting how classical laws often sharply contrast with common practices today. Freidenreich said, “How we eat reflects how we think about ourselves and those around us.”

Many religions maintain stringent rules on how, what or when people may eat—practices that both serve to unite members of a sect and to separate them from those with different customs. Even within a single religion, rituals differ because of varying interpretations of a religious text. The “nature and significance of Christian, Islamic and Jewish foods have shifted over time,” Freidenreich said.

Originally, according to Freidenreich, the Jewish custom of keeping kosher did not encourage separation from non-Jewish eaters and was simply a matter of preparation. “By keeping kosher, Isrealites confirmed their status as holy, but they could eat with anyone.” Eventually, however, “keeping kosher wasn’t just about ingredients of the food but about who prepared it and shared it,” he said. The shift occurred as conflicting interpretations of the Bible and Torah arose, and the emergence of Christianity created a schism in the way people shared food.

Each group frustrated with the other, Christians began to define themselves as anti-Jews and structured their differences around food. “If Jews ate it,” Freidenreich said, “Christians wouldn’t.” Though Islamic doctrine closely ties into Christianity and Judaism, conflict remained between all three major groups, and even within Islam, as the Shiites and Sunnis split into two sects.

In the past few centuries, secular ideas have melded religions together more, so that in many areas people of different religions can exist—and even eat together—in peace (indeed today you would, and often do find priests, ministers and rabbis sharing a meal). Nevertheless, religion remains a driving influence behind many people’s lifestyles and choices. Freidenreich said that “the ideal of a melting pot, in which religion would disappear, is being replaced with the idea of a salad bowl,” in which distinctions would remain and be celebrated. Whether “distinctive or self-segregating, food is defining [of] identity,” Freidenreich said.