Once every few years, someone suggests writing a constitution for Israel. Now, the would-be politician Yair Lapid has joined them, saying he promised his son Yoav "some sort of state," and wants to keep his promise before he dies. As usual, Lapid is playing it safe: The generic call for a constitution is very popular among the populists of the centrist parties, who can pretend they are conducting a public campaign without actually saying a thing.

Nearly every country in the world has a written constitution, and the absence of an Israeli constitution is depicted by those who favor drafting one as a fundamental flaw in our system of government. It is portrayed as yet another expression of the improvisational style that is our typical substitute for order, organization and waiting in line. "There is no country without a constitution," screams the Web site of Constitution by Consent, which is backed by the Israel Democracy Institute. Promoting a constitution is viewed by its supporters as an expression of normalcy, as something good and desirable - what the Americans describe as "motherhood and apple pie," or like the world peace that beauty-pageant contestants promise to promote if they win the crown.

But the question is not whether we need a constitution, but what will be written in it and how will it be implemented. A constitution entails decisions on fundamental questions of national identity, and for the most part serves the interests of society's stronger groups, under the cover of noble values. The existence of a constitution does not ensure that the regime will be democratic or that it will preserve citizens' rights. The Syrian constitution, for example, is far more committed to freedom of expression and freedom of the press than Israeli law, but it is still better to be a journalist in Tel Aviv than in Damascus.

David Ben-Gurion gave up on a written constitution in the state's infancy. This decision stemmed from three factors: a surrender to the religious parties, which have always opposed a secular constitution; the founding father's desire to include everyone under the same national tent, instead of imposing the majority's positions on minorities; and his assessment that the absence of a constitution would serve his Mapai party and keep it in power better than a liberal document committed to citizen rights would.

However, the result has not been bad. The improvised system that Ben-Gurion established developed into an open and raucous democracy, despite its shortcomings of discrimination against minorities and the military's excessive power - which would have existed even with a constitution.

In recent years, various proposals for an Israeli constitution have been published. They fall into two categories: those that take sides in the debates between religious and secular and between Jew and Arab - "who is a Jew?" and "who is a citizen?" - and those that try to offer a compromise.

But what constitution does Lapid want? The Adalah draft, which wants to do away with the land laws that enabled the state to take over millions of dunams of land that belonged to Arabs before 1948? The Institute for Zionist Strategies draft, which calls for more land to be given to Jewish settlements? Does he prefer Constitution by Consensus, which seeks to preserve the status quo against the pressure of social change and the growing strength of the ultra-Orthodox and Arabs? Or perhaps he does not care, so long as there is a document called a constitution?

All the alternatives are problematic and dangerous to democracy. A constitution that decides fundamental questions of national identity will cause internal divisions, especially in the current political climate, in which the right is trying to crush the Arab community's power. But a constitution that seeks a broad compromise will at best not change a thing, and at worst will bolster the status of the religious and Jewish law.

Constitution by Consensus, backed by former Supreme Court president Meir Shamgar, promises "stability, public transparency, equality and unity." To get there, its authors offer the religious a deal: closing down malls on Shabbat and preserving the rabbis' control over marriage and divorce in exchange for "civil unions" - a second-class form of civil marriage. If this is the constitution they are offering, it would be best to give up and stick with Ben-Gurion's tradition of no constitution. This was also Ariel Sharon's position.

Instead of the empty process of talking about "writing a constitution," Lapid would do better to prepare a draft and clarify what he plans to fight for. How will the state he has promised his son Yoav look? What will its borders be, who will its citizens be and what rights will they enjoy?

If he offers answers and fights to achieve them, there will be a point to him joining politics. If he makes do with empty slogans, it would be best if he stuck to his television program.