The “two state solution” to the Israel/Palestine conflict has become the glamourless default position of most of those who think about the conflict. It has achieved that lumpy status despite the flaws in its logic, the problematics of its implementation, the dangers that inhere in it and the determined hostility to it from some on both sides of the conflict. Still, it’s been the only end game in town for quite some time, and it has had as its foundation stone the belief that only with two viable states can Israel preserve itself as both Jewish and democratic.

The late-19th- early-20th century economist E.R.A. Seligman once said of the property tax that it was an excellent device, except for the fact that it was wrong in theory and could not work in practice. A growing and very disparate assembly of Israelis and Palestinians has now, in effect, taken to using the same argument with regard to a two-state solution, and there has suddenly emerged a pro-one-state camp.

In one sense, the idea of a unitary state from the Mediterranean to the Jordan is not new. It had a modest run in the 1920s and 1930s, back then endorsed by such Zionist luminaries as Henrietta Szold, the founder of Hadassah; Judah Magnes, president of the Hebrew University, and Martin Buber, the eminent philosopher. It flared briefly into view in the 1970s, when Yasir Arafat urged that “all” of Palestine be transformed into a “secular, democratic state.” It has been a constant of some on the left all the while — and, more recently, and perhaps most notably, advanced Tony Judt, the historian, whose untimely death we mourn. This camp saw Israel, as Judt put it in 2003, as “an anachronism,” saw little virtue and much vice in the admittedly amorphous idea of “a Jewish state.”

But now, almost overnight, there has emerged a cohort of Israelis who believe that only via a one-state solution can Israel remain both democratic and Jewish. This unexpected development was kicked off by former minister of defense Moshe Arens in an opinion piece in Haaretz just two months ago. That is important, because it means that the lead is not being taken by the Orthodox settler camp, who believe that the Jews are divinely mandated to control the whole of the Land of Israel, but by people like Arens and Knesset speaker Reuven Rivlin, secular Jews who are uncomfortable with the 43-year-long occupation of the West Bank and recognize that the international community is increasingly impatient with it; who have no confidence that negotiations for a two-state solution can succeed or, if they do, that the resultant states can live amicably with each other; and — here’s the kicker — who believe that in the one state they champion, Jews can still be the dominant force.

How can that be? Has not the key argument of the two-staters been the demographic argument — that is, that in the area between the Mediterranean and the Jordan River, the number of Palestinians (given their higher birth rate) will in the foreseeable future outnumber the Jews? That persistent concern gives rise to a variety of plans, most of which defer the granting of full citizenship to Palestinians in the new enlarged state to a future time — a generation, perhaps — and perhaps even to require all citizens to swear their loyalty to what these one-state advocates continue to define as a Jewish state. Other one-state advocates work with the numbers, purport to show that without Gaza, and not counting those Palestinians who might choose to return from their diasporas, Jews will continue to be the majority — not the 80% majority they are today, but a comfortable 60% majority.

This last is the clearest indication of the foolishness of the one-state argument. Today’s 20% Palestinian minority holds 14 Knesset seats (four as members of “Jewish” parties); were Palestinians in fact a 40% minority in the new state, they would — if they were mobilized — be able to control up to 48 seats in the 120-member Knesset. To put that into some kind of perspective, the largest party in the current Knesset, Kadima, holds 28 seats; the largest party in the governing coalition, Likud, holds 27; Labor holds only 13. A sizeable Palestinian minority might not be able to govern, but might easily emerge as a blocking force. (The Republicans in the U.S. Senate hold 41 of the 100 seats and know something about blocking.)

A one-state solution is inherently a political disaster, a recipe for permanent divisiveness and conflict. However it starts out, there will early on be robust calls to limit Palestinian political power — that is, to limit the definition of “citizenship” as it applies to Palestinians. Jewish and democratic? Take your pick; you can’t have both. (And you might well end up with neither.)

Back, therefore, to two states. And back, therefore, to President Obama, whose determination to prod the parties into a two-state agreement is the hot engine of the day as it stubbornly seeks to pull cars that are either cold or at best tepid. Two states? Not a perfect solution, merely the only one that makes sense. Oh yes: Seligman turned out to be wrong about the property tax.