According to a well-known legend, Napoleon once passed a synagogue on Tisha B'Av and was taken aback upon hearing sounds of weeping and lamentation.

When told that the mourners were grieving the Temple's destruction from two thousand years earlier, he reportedly remarked with admiration that a people capable of mourning such an ancient loss would one day restore what had been lost.

In this story, memory serves as a power for renewal.

But this year, on Tisha B'Av 5786, we must worry that we have forgotten. We will fast and observe the practices of our national day of mourning. We will go through the motions, yet the conclusion is unavoidable: we have forgotten.

Jewish tradition links the loss of sovereignty in our two prior commonwealths to internal hatred, which weakened the Jews' capacity to resist their foes.

The burning of Jerusalem's granaries amid an enemy siege remains the clearest emblem of the folly to which fraternal hatred can lead.

Today, too, we risk igniting the granaries of sovereignty - undermining the rule of law, eroding trust in state institutions, and weakening governance - once again, while engaged in conflict with our enemies.

According to a recent JPPI survey, a majority of Israelis (55%) believe that the greatest threat to our future lies not beyond the country's borders - in security threats and global antisemitism - but within us.

In their view, the chief danger comes not from Mojtaba Khamenei or Zohran Mamdani, but from the choices and actions inside our shared home. That intuition is not unfounded, but it requires precision.

The danger does not stem from disagreement itself, but from the way we manage it. Public life has become an arena for a zero-sum game: either I prevail, or I am defeated. Each camp is thoroughly convinced that the other side's victory would make our shared home unlivable.

This apocalyptic reading of reality - to which many have become addicted - is fertile ground for fanaticism. And fanaticism, as Jewish history teaches, is the true battering ram against the walls of sovereignty.

Disagreement is not a defect to be corrected; it is an inseparable part of a living society. The real question is whether we can disagree without negating the legitimacy of the other side, without turning it into an enemy to be crushed.

This requires empathy - not agreement. Empathy means recognizing that those who think differently from us also act from a worldview, a set of values, and a sincere concern for the country's future.

Try a painful exercise: if you vote on the Left, are you prepared to say that Bezalel Smotrich may be wrong, but seeks the good no less than you do? If you vote on the Right, can you say the same of Yair Golan? My guess is that each side is offended by the very comparison. And that is precisely the problem.

A 'thin constitution'

Empathy alone, however, is not enough. A polarized society needs agreed-upon rules of the game for managing its disputes.

Israel needs a thin constitution - a basic constitutional framework that would establish a durable consensus on how public life is conducted.

Had such a framework been in place, it would have blocked the kind of sweeping constitutional overhaul attempted by the outgoing coalition.

It would likewise dispel the mirror-image fear that, if today's opposition wins the next election, it will impose an overhaul - a political revolution - of its own.

In the absence of agreed-upon rules for managing disagreement, each side fears that if it does not vanquish the other today, it will be trounced tomorrow.

That fear creates a vicious cycle in which each camp uses its power to remake reality unilaterally in its own image - and in doing so assails the walls of Jerusalem in our generation.

The three weeks between Tamuz 17, when the walls of Jerusalem were breached, and Tisha B'Av, when the Temple was destroyed, are known as Bein HaMetzarim - Between the Straits.

The phrase comes from the Book of Lamentations (1:3): All her pursuers overtook her in the straits.

How tragic that the pursuers threatening our future, then as now, are ourselves. Will we know how to remember what fanaticism wrought in earlier generations and break the curse?

After the election, we can begin repairing the damage by binding ourselves to entrenched rules for managing our disagreements - a thin constitution.

The writer is president of JPPI - the Jewish People Policy Institute - and a professor (emeritus) of law at Bar-Ilan University.