One of my favorite concepts in logic is the reductio ad absurdum (Latin: “reduction to the absurd”) argument, which is a logical method of argument that proves the falsity of a premise by following its implications to a logical but absurd conclusion.
The latest news regarding the nullification of one the United States’ most prestigious and venerable rabbis of the United States, Haskel Lookstein, is the rabbi who converted Donald Trump’s daughter Ivanka, and officiated at Ms. Trump’s wedding to Jared Kushner in 2009.
What triggered this conundrum?
Back in April, a small rabbinical court the city of Petach Tikvah (near Tel Aviv) rejected Rabbi Lookstein’s the conversion of a woman named Nicole, who underwent conversion under his auspices. When she applied for marriage registration with her Israeli fiancé, Lookstein’s name did not on the pre-approved list of rabbis’, whose conversions are acceptable by the Chief Rabbinate.
One thing led to another and the rabbinate decided to invalidate all of R. Lookstein’s conversions, which include Ivanka Trump, the daughter of business magnate and presumptive Republican presidential candidate Donald Trump.
The Israel Times report details what happened in the first hearing that took place last week when the Supreme Rabbinical Court reinforced the opinion of the Petach Tikvah lower court. To make a long story short, they denied this woman and others their conversion—despite the fact that Israeli Ashkenazi Chief Rabbi David Lau approved of all Lookstein’s conversions. Knesset Speaker Yuli Edelstein also said that the Chief Rabbinate recognizes Lookstein’s conversions.
Negating conversions are nothing new in modern Orthodoxy today. A few years ago, the Haredi rabbis and their political allies threatened to overturn over 15,000 conversions of Rabbi Chaim Druckman, who served as the acting director of the National Conversion Authority in Israel.
For over two thousand years rabbis have respected the right for rabbis in other localities to make decisions for their own communities with complete autonomy. Rabbis who differed with their colleagues on halachic issues generally treated one another with respect and dignity. Unanimity and conformity to a single Halachic standard went against the belief that every community had the right to follow its own traditions and rabbis—even if some of these rabbis followed a minority opinion at times.
But today, we are living in a very different world indeed.
Let me briefly explain why revoking a conversion is wrongheaded and scandalous.
The concept of revoking a conversion is a recent innovation in rabbinic law. As we have posted in other places, the Shulchan Aruch (Code of Jewish Law) does not sanction revocation of conversions at all. Should a convert return to his former gentile roots, the halacha still considers him as a “sinful Israelite.” 
Simply stated, revoking conversions is risky business and can cause unspeakable harm to countless innocents who are indirectly or directly triangulated in the rabbinic web the Haredi rabbis have woven.
Reductio ad absurdum in Action
Here is a hypothetical story to consider.
Once upon a time, a woman converts from Catholicism and became a pious Haredi Jewess at the tender age of 20. She raises a family of twenty children. The next generation has the same number of children, as does the third and fourth generation of Haredi Jews. All of them are pious and God fearing Haredim.
By the time this woman reached her 120th birthday, she produced approximately 20x20x20x20 = 160,000 people–not bad for this one prolific Jewish mother!
But something unpredictable happened.
At this matriarch’s 120th birthday, the original convert decides to return to her original Catholic faith on her 120th birthday…
See the problem?
That decision, according to Haredi logic, would jeopardize the Jewish status possibly of up to four generations of Haredi Jews, equaling more than 160,000 Jews! That would mean all of her offspring numbering 160,000 people would all be technically Haredi Gentiles! Our little reductio ad absurdum argument explains why our rabbinic ancestors had the common sense not to revoke conversions. Rather, they considered the wayward convert as a “cho’te Yisrael” ( a “Jewish sinner”) and left it at that.
Ethically and halachically, children especially must not be penalized for the sins of the parent, our tradition teaches us. Creating artificial halachic barriers will not solve the problem, it will only compound it–even lead to an exponentiation that will create a scandal for everyone.
I believe the Haredi community has every right to define whom they wish to recognize as a bona fide member of their specific community. However, these Haredi rabbinic leaders do not have the right to legislate for communities outside of its jurisdiction. Every community has the right to decide for itself. That has always been the case in the history of Jewish law. Every community is autonomously responsible for its members.
The fact that all of this is happening near the time of the Three Weeks when Jews are supposed to get along with one another is upsetting and contrary to the spirit of our tradition demands we make the effort to co-exist peacefully and respectfully together.
Let us hope that the Modern Orthodox rabbinate in the United States and elsewhere in the Diaspora will join the ranks of the Conservative and the Reform in implementing a separation of Synagogue and State, lest we become a mini-me version of the Islamic fanatics who rule oppressively by the force of theocratic law.
We have enough enemies to deal with, we should not be fighting among ourselves.