During a debate in Brandeis with a popular leftist “rabbi” named Axelrod, Meir Kahane objected to him conducting marital ceremonies for interfaith families. In Kahane’s opinion, rabbis must deal with traitors unequivocally, setting before them the choice to remain among Jews or leave us. On a personal level, I sympathize with Kahane’s position. To me, intermarriage is revolting because it finishes the Nazis’ job. It does not matter whether a Jew’s line is terminated in an oven of Auschwitz or the melting pot of New York—the bottom line is the same.

Still, I understand Axelrod’s reasoning, which is shared by many conservative rabbis. Often the non-Jewish spouse in an interfaith family has no faith, and can be won over to lead a nominally Jewish life. Jewish, that is, by conservative and reform standards, which demand little more than a Chanukah chandelier beside the Christmas tree. Nevertheless, many gentile spouses observe Jewish traditions as much as their Jewish partners.

The Torah is straightforward on this: a eunuch shall not enter the assembly of the Lord. Why? People of other bodily defects are allowed into the Temple. What makes a eunuch different is that his procreative function is damaged. The Torah likewise declares the spilling of seed to be unclean. Importantly, there is nothing wrong in the Torah’s eyes with seed-spilling or castration per se: they only cause impurity, and only for Jews. It follows that the Torah detests any actions which harm specifically Jewish procreation. Since a Jew who enters into an interfaith marriage won’t be producing Jewish children, he must be treated like a eunuch, and expelled from Jewish congregations. Interfaith marriages, of course, must not be confused with marrying a convert to Judaism, even a likely or de facto convert.

Intermarriage is a function of society’s openness. For small groups, the intermarriage rate is necessarily high. In America, Jews constitute 1.5 percent of the population. Accordingly, a mere 1.5 percent intermarriage rate for gentiles translates into a 100 percent intermarriage rate for Jews. In other words, too many prospective gentile spouses compete for a limited number of Jews, and Jews have tremendous choices of marriage opportunities with gentiles, compared to their limited choices among other Jews.

Intermarriage in America runs at 70-90 percent among non-Orthodox Jews. Diminishing it won’t help. Even at a 30 percent intermarriage rate, the number of Jews would dwindle by two-thirds in just three generations (if you remember your school math, that’s (100-30)%3=35%).

The Conservative Movement dropped the Torah’s ban on intermarriage, ostensibly as an emergency measure to preserve the Jewish people. Sure enough, they cared more about reaching out to potential donors than about Jewish survival. It may be that their permissive attitude toward intermarriage does not actually encourage many Jews to form interfaith families: typical members of conservative congregations care very little about Judaism, and certainly won’t shrink from intermarriage because of the opinion of their rabbi, for whom they usually harbor as much respect as for a waiter or any other paid servant – because they pay his salary. But rabbinical permissiveness likely encouraged many interfaith families to abandon Jewishness altogether: if a gentile spouse is welcome at the local synagogue, why bother raising the kids Jewish? Gentile partners, too, see that rabbis make no distinction between them and Jews, and feel no urge to behave in a Jewish way.

Not all the lost sheep are lost, and Jews must reach out to our intermarried brethren and possibly convert some interfaith families. Community rabbis, however, must not be involved in this questionable proselytizing work, and certainly cannot officiate at interfaith marriages.