Vital messages sometimes lie in silent gaps. Like the dearth of any mention in the Torah of Shavuot's connection to the giving of the Torah at Mt. Sinai. That silence, writes Rabbi Samson Raphael Hirsch, powerfully communicates a critical Jewish fact: The Oral Law - the meticulously transmitted non-written Jewish religious tradition - is indispensable. Without it, we cannot even place the Torah's revelation in time. The Oral Law's indispensability is evident throughout the Judaism to which we are heir. Never was "an eye for an eye" (Exodus 21:24) understood by Jews literally; the Oral Law informs us that its true intention is monetary compensation. The "frontlets" Jewish men are to place "between your eyes" (Deuteronomy 11:18) are placed not between anyone's eyes but above our hairlines (current or erstwhile). And what's a "frontlet" anyway? Or, for that matter, a totefet? Similar keys to Jewish truths unlock the Prophets and Writings portions of Judaism's canon no less. Including narratives like the conversion of Ruth, the biblical heroine whom Conservative Rabbi Reuven Hammer ("In praise of conversion," June 1) has humorously imagined applying for Jewish status in modern-day Israel. Humor can be entertaining and even enlightening, of course. But here it also misleads. Yes, bureaucracies and government functionaries are recently evolved entities, and at times problematic ones. But we do have a clear oral tradition about Ruth's conversion: It entailed precisely what contemporary conversion entails, whether or not she had to take a course or fill out forms. And prime among the things she had to do - indeed, the sine qua non of Jewish conversion before and after her time - was to sincerely accept the responsibility to observe all the Torah's laws (kabbalat hamitzvot). A convert need not be conversant with all the laws at the time of conversion but he or she must nevertheless embrace them in principle, fully and honestly - just as our ancestors did at Sinai when they declared "we will do" before "we will hear" (Exodus 24:7). In fact, various Jewish conversion laws are evident in the actions and words of Ruth and Naomi. Naomi's discouragement of her daughters-in-law, for instance, reflects the halachic imperative to discourage potential converts. And Ruth's words to Naomi are parsed by the Talmud to refer to her acceptance of Jewish observances. Hammer is correct that a properly conducted conversion cannot be "retroactively cancel[led]." If a convert decides to abandon his or her previous acceptance of mitzvot, he or she is a lapsed Jew like any other. If, however, it is demonstrated, even at some later date, that there never was kabbalat hamitzvot at the time of the conversion ceremony (or that some other required element of conversion was missing), then there was, simply put, no conversion to begin with. I DO NOT and cannot speak from personal knowledge of any particular conversion or set of contemporary conversions. What I can state is that considering a lack of kabbalat hamitzvot to undermine a conversion is not some "draconian" or "political" invention born of "pressure from haredi rabbinical groups in Europe." It is Jewish religious law, as always it was. There are certainly non-Jews in Israel who sincerely wish to wholeheartedly join the Jewish people and its mission. When they convert, with acceptance of the mitzvot, they will be considered Jewish by all Jews, as are all halachic converts. But there are many non-Jews in Israel, among them hundreds of thousands of immigrants from the former Soviet Union, who may see some benefit in being considered Jewish but who have no interest in undertaking Jewish observance. Hammer, lamenting that "we are now a small people," wishes that they be enticed to undergo a conversion ceremony and be welcomed into the Jewish people. As a non-Orthodox rabbi, he is not constrained by the requirements of Halacha. Indeed, he dismisses the Oral Law's teachings about how conversion took place in biblical times as "fanciful"; and declares his belief that in the time of Ruth "conversion as we know it [i.e. as Halacha has it] did not exist." But there are those of us who affirm the entirety of the Jewish religious tradition. And we are not just haredim and not just "centrist" Orthodox Jews. A majority of Israeli Jews (both the personally observant and many who are not so) feel the same. What is more, even leaving aside the theological issue of Jewish religious law "as we know it," eroding the requirements of Halacha would cause terrible harm to the Jewish people. Think ahead a generation. Children of the beneficiaries of "relaxed conversion standards" might one day become observant and come painfully to discover that they are suddenly not Jewish by the measure of their own beliefs. They (and, if they are women, any children they may have had in the interim) will have to undergo a halachically valid conversion. Worse, women among them engaged to kohanim would discover that, as new converts, they cannot halachically marry their fiancÃ©s. And, worst of all, the Jewishness of every convert and convert's child would be suspect to all Halacha-respecting Jews. Only a universally accepted conversion standard can ensure that converts are embraced as Jews - as they should be - by all other Jews, and prevent the Jewish people from becoming, God forbid, a multitude of "Jewish peoples." That standard is the halachic one. Wishing it away is wishing for the utter undermining of what is left of the Jewish unity forged at the foot of Mt. Sinai 3321 years ago. The writer is director of public affairs for Agudath Israel of America and the author of a biography of a convert to Judaism, Migrant Soul: The Story of an American Ger.