And lest one imagine that this is just another battle between the more progressive Reform and Conservative denominations and the more observant Orthodox, it must be noted that the criteria used by the rabbinate are driven by internal Haredi politics, not observance. According to the Jewish Week, at one point the number of American rabbis who were officially authorized by the Israeli rabbinate to perform conversions was down to a few dozen. Even if you are Orthodox  and especially if you are Modern Orthodox  your rabbi probably doesn’t make the cut. (Don’t believe it? Go ask him.)

Given that the conversion bill is the latest in a series of similarly motivated efforts, it seems almost useless to note that the stringent approach to Jewish law that the Israeli rabbinate promotes bears little connection to the historical experience and religious practice of the majority of Jewish people over the past two millenniums. It will do little good, too, to point out that it is well outside the consensus established by Hillel  arguably the greatest rabbi in all of rabbinic Judaism and whom, as Joseph Telushkin argues in a forthcoming book, was willing to convert a pagan on the spot, simply because he’d asked.

And it doesn’t help to argue that giving the ultra-Orthodox rabbinate total control over Jewish practice will destroy religious life in Israel just as surely as clerical control hurt the Church of England and the Catholic Church in Spain and France. Or that the Zionist founders, from Herzl to Jabotinsky to Ben-Gurion, all believed passionately in the unity of the Jewish people and the need for a secular state.

But perhaps a more practical rallying cry will work: If this bill passes, future historians will inevitably wonder why, at a critical moment in its history, Israel chose to tell 85 percent of the Jewish diaspora that their rabbis weren’t rabbis and their religious practices were a sham, the conversions of their parents and spouses were invalid, their marriages weren’t legal under Jewish law, and their progeny were a tribe of bastards unfit to marry other Jews.

Why, they will wonder, as Iran raced to build a nuclear bomb to wipe the Jewish state off the map, did the custodians of the 2,000-year-old national dream of the Jewish people choose such a perverse definition of Jewish peoplehood, seemingly calculated to alienate supporters outside its own borders?

And, they will also wonder, what of the quiescence of diaspora Jewry? Many American Jews understandably see Israel as under siege and have not wanted to make things worse; they imagined that internal politicking over conversions and marriages was ephemeral, and would change. But the conversion bill is a sign that this silence was a mistake, for it has been interpreted by Israeli politicians as a green light to throw basic questions of Jewish identity into the pot of coalition politics.

The redemptive history of the Jewish people since the Holocaust has rested on the twin pillars of a strong Israel and a strong diaspora, which have spoken to each other politically and culturally, and whose successes have mutually reinforced the confidence and capacities of the other. Neither the Jewish diaspora nor Israel can afford a split between the two communities  a dystopian possibility that, if this bill passes, could materialize frightfully soon.