Unlike Buddhism, Christianity and Islam, Judaism does not have a missionary impulse. That is why there are so few Jews in the world. Mormons, who very actively seek converts, already outnumber Jews even though Mormons have been around less than 200 years; compared to more than 3,500 years for Jews.

Of course, Judaism has no missionaries in world wide distant lands, while according to the Mormon newspaper, the Deseret News (August 2013); there are now more than 75,000 Mormon missionaries in the field worldwide, and more than 85,000 missionaries are expected to have entered missionary service by the end of 2013.

This compares to only a few hundred Jewish outreach personal; who mostly confine their efforts to seeking out only non-Jews with Jewish ancestry.

Almost all Jews are proud of Judaism’s lack of missionary zeal, but very few Jews are aware of the heavy price Jews have payed both historically and biologically for going far beyond neutrality; and actively discouraging non-Jews from becoming Jewish. In Israel, where we have exact figures, the situation is steadily getting worse.

The state-run, ultra-Orthodox controlled, Conversion Authority works slowly and bureaucratically, deterring hundreds and thousands of immigrants from the former USSR, who have Jewish lineage but who are not halachically Jewish. In 2011 the state’s Conversion Authority performed just 4,293 conversions, down more than 45% from 8,008 in 2007.

The decline was not a fluke. It was a policy of increasing exclusion as the numbers prove: from 8,008 in 2007 to 6,221 in 2,008, down to 4,645 in 2010. (Orthodox Rabbi David Stav in The Jewish Daily Forward 4/9/13.

How has making conversion difficult hurt the Jewish People?

Ashkenazi Jews have an unusually high risk of several genetic diseases compared to their non-Jewish neighbors , and up until now, no one understood why. Disease mutations unusually common in Ashkenazi Jews are: Tay-Sachs disease, some forms of breast cancer, high cholesterol, hemophilia and several less known diseases.

So why did the percentage of Jews with these genetic defects increase compared to their surrounding non-Jewish populations?

According to Dr. Neil Risch, professor of genetics, at Stanford University School of Medicine, these mutations were probably present in the Jews who coalesced into the Ashkenazi Jewish population over 900 years ago. Jewish parents passed the mutations along to their children because Ashkenazi Jews in the 12th to 15th century all married within their own small population.

But, and here is how history enters into the picture, it is also true that European Jews were prohibited by the Church from accepting converts to Judaism, who would have reduced the chances of inheriting genetic defects.

Both in-marriage and lack of fresh blood (both physically and spiritually) from converts to Judaism were factors contributed to keeping those mutations common.

The final mutations for Tay-Sachs cropped up in Lithuanian Ashkenazi Jews about 12 generations ago. All of these mutations would have been reduced by the entry of non-Jews into the Jewish gene pool through conversion to Judaism.

Because conversion was severely restricted by the European Church from the 4-6th century on, converts to Judaism were not able to help eliminate these harmful genetic mutations.

If there is a substantial rise in conversion to Judaism in the 21th century, these harmful mutations will substantially decline by the end of this century. But, will there be a significant rise in the number of converts?

Judaism lacks a strong missionary impulse because Judaism is a pluralistic religion. Judaism teaches that the Jewish way is right for us, but good people in other religions also have a place in the world to come. Correct behavior in society is more important than correct beliefs about God.

Thus, while Jews should welcome non-Jews to join us, many Jews, including some rabbis, see no reason to encourage conversion; and so do not welcome interested non-Jews who desire to become Jewish.

Lacking the missionary impulse of more universalistic religions, Jews react to potential converts in varied ways, ranging from wariness to encouragement. Practical community concerns guided many of out Sages.

Some like Rabbi Helbo said that converts are an irritation like an itch, a sore or a scab. Perhaps Rabbi Helbo felt that the enthusiasm and idealistic expectations of converts irritated too many born Jews, who take their Jewishness much more casually. Or maybe he agreed with Rabbi Isaac who said “Evil after evil comes upon those who receive converts”.

Both these Rabbis lived in the early 4th century when the Church was vociferously attacking pagans who choose to become Jews rather than Christians. Perhaps they feared Christian anti-Semitism if Jews openly received converts.

On the other hand, Rabbi Simon ben Lakish proclaimed that a convert is more beloved to God than all the Jews who stood at Sinai. This seems rather extreme. Perhaps he was reacting to those who claimed Jewishness was in their noble genes.

Equally amazing were Rabbi Eleazar ben Pedat and Rabbi Yohanan who both taught that the forced exile of the Jewish people among the Gentiles was really a God given opportunity to influence Gentiles to become Jewish.

Some Rabbis tried to test the sincerity of potential converts by making great demands of time and effort from them. Opposing this Rabbi Johanna advises that you should push potential converts away with your left hand and draw them close with your right hand.

Since most people are right handed if you actually push away more than a few non-Jews you are being too negative.

Rashi, the greatest of our Bible commentators, taught that Jews started seeking converts from the very beginning, when he interpreted a verse that states that Abraham made souls in Haran, to mean that Abraham and Sarah made converts.

And the Talmud (Sanhedrin 99b) condemns those who push potential converts away by relating that Isaac and Jacob pushed away Timna the sister of Lotan who wanted to become Jewish. She then married a son of Esau. One of her descendants was Amalek who attacked Israel shortly after they escaped from Egypt. If, instead of being pushed away, Timna had become Jewish, Amalek would have been on our side, and not one of our enemies.

Indeed, Rabbi Yohanan says the Jews were oppressed and enslaved in Egypt because Abraham didn’t try to influence some captives that he rescued to become Jewish. (Neddarim 32a) Even failing to encourage potential converts is wrong according to Rabbi Yohanan.

Several other Rabbis felt that discouraging converts in the past had brought troubles upon us. These are practical, not theological, reasons to seek converts and not to push away those who might be interested.

Rabbis today should welcome potential converts and not discourage them. We may not be saving souls, but we should not be making future enemies by rejecting people who want to be Jewish.

Rabbi Maller’s web site is: rabbimaller.com