You see a barrier in the West Bank city of Hebron, with barbed-wire coils, hills scarred by patrol roads and weather-beaten guard posts, Israel has been shaped like few other countries by its borders.

True believers in the two-state solution see absolutely no hope elsewhere.

With no alternative in mind, and unwilling or unable to rethink their basic assumptions, they are forced to defend a notion whose success they can no longer sincerely portray as plausible or even possible.

It’s like 1975 all over again, as the Spanish dictator Francisco Franco fell into a coma:

The news media began a long death watch, announcing each night that Generalissimo Franco was still not dead. This desperate allegiance to the departed echoes in every speech, policy brief and op-ed about the two-state solution today.

True, some comas miraculously end (Not Sharon).

Great surprises sometimes happen. The problem is that the changes required to achieve the vision of robust Israeli and Palestinian states living side by side are now considerably less likely than other less familiar but more plausible outcomes that demand high-level attention but aren’t receiving it.

Strong Islamist trends make a fundamentalist Palestine more likely than a small state under a secular government. (Not feasible: Palestinians are the most educated people in Near East)

The disappearance of Israel as a Zionist project, through war, cultural exhaustion or demographic momentum, is at least as plausible as the evacuation of enough of the half-million Israelis living across the 1967 border, or Green Line, (600,000 just in the newest settlements) to allow a real Palestinian state to exist. While the vision of thriving Israeli and Palestinian states has slipped from the plausible to the barely possible, one mixed state emerging from prolonged and violent struggles over democratic rights is no longer inconceivable.

The fantasy that there is a two-state solution keeps everyone from taking action toward something that might work. (Like what other alternatives?)

All sides have reasons to cling to this illusion:

1.  The Palestinian Authority needs its people to believe that progress is being made toward a two-state solution so it can continue to get the economic aid and diplomatic support that subsidize the lifestyles of its leaders, the jobs of tens of thousands of soldiers, spies, police officers and civil servants, and the authority’s prominence in a Palestinian society that views it as corrupt and incompetent.

2. Israeli governments cling to the two-state notion because it seems to reflect the sentiments of the Jewish Israeli majority and it shields the country from international opprobrium, even as it camouflages relentless efforts to expand Israel’s territory into the West Bank. (That’s not true, this clinking argument, otherwise it would have taken place 10 years ago…)

3. American politicians need the two-state slogan to show they are working toward a diplomatic solution, to keep the pro-Israel lobby from turning against them and to disguise their humiliating inability to allow any daylight between Washington and the Israeli government.

4. Finally, the “peace process” industry — with its legions of consultants, pundits, academics and journalists — needs a steady supply of readers, listeners and funders who are either desperately worried that this latest round of talks will lead to the establishment of a Palestinian state, or that it will not.

Conceived as early as the 1930s, the idea of two states between the Jordan River and the Mediterranean Sea all but disappeared from public consciousness between 1948 and 1967.

Between 1967 and 1973 it re-emerged, advanced by a minority of “moderates” in each community.

By the 1990s it was embraced by majorities on both sides as not only possible but, during the height of the Oslo peace process, probable. But failures of leadership in the face of tremendous pressures brought Oslo crashing down.

These days no one suggests that a negotiated two-state “solution” is probable. The most optimistic insist that, for some brief period, it may still be conceivable.

A version of this op-ed appears in print on September 15, 2013, on page SR1 of the New York edition with the headline: Two-State Illusion.