Sometimes a straight answer helps

[redbird]

A pointer on metaquotes somehow turned into a more-heat-than-light discussion of circumcision. Somewhere in there, someone asked the reason for the Jewish custom of circumcision, and wanted to know whether it was in the Torah.

I decided they might be serious, and said yes it is and mentioned Abraham and Isaac. They thanked me. Apparently, despite knowing the word "Torah", they had never heard that story.

There's an awful lot to know--thousands of years of history, culture, technology, myth, science, and general weirdness inevitably lead to that--which in turn means that there's probably nothing that everyone knows.