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“Any time young people approach me in order to get married, I ask them various questions about their future. Eighty percent of them say they do not envision any future in France.” This is what one rabbi in Paris told me last week. I heard similar statements from other French rabbis and lay Jewish leaders: “We have a feeling the words are on the wall now,” one leader in the Lyons area confided to me. “It is not just our situation in this country deteriorating; it is also that the process is much quicker than expected.”

Even the chief rabbi of France, Gilles Bernheim, may be sharing that view now. A philosopher (holding a prestigious French agrégation degree in philosophy), a graduate of the French Rabbinical School in Paris, and a former student at some...