In the aftermath of last week’s surprisingly upbeat Annapolis meeting, all the talk’s about a two-state solution. The unwary may suppose that as soon as the domestic problems within Israel and among the Palestinians are resolved, the movement toward such a solution will be quite rapid.

After all, we’ve been repeatedly told that the essential parameters of the two states are widely known and essentially shared. Call them “the Clinton parameters,” or Taba, or Geneva; the only things now standing in their way are the legacy of mutual bitterness, the political weakness of the leadership on both sides and, of course, the passions of the “maximalists,” those who believe that one or the other people can and should dominate the land between the Mediterranean and the Jordan River.

Would that were so.

Not only are those “only things” very big things, but there’s one other point that’s often forgotten: When you start examining the nuts and bolts of a renewed partition of the land, of two viable states living next to each other in peace and security, you find yourself in a hornets’ nest of complication.

Some examples: What shall be done about controlling the eastern boundary of an independent Palestine? Shall the Palestinians themselves be enabled to decide who gets into their country? They surely believe they should be, and the logic of independence supports their view.

But the accumulated suspicions generated these last decades suggest that Israel dare not abandon its control of access lest, over time, terrorists enter Palestine and await their chance to do harm to Israel. Some have suggested that Israel be granted a long-term lease — say, 25 years or so — to the Jordan Valley, or that some sort of international presence be situated there. The problem is not a deal-breaker, not by itself, but neither is it a trivial obstacle.

Nor is the Jerusalem problem. Once again, we get stuck on the question of access. Of course the permanent solution will involve sharing the city so that it may serve as capital of two states.

But will there be an international boundary, with border controls, snaking through Jerusalem’s neighborhoods? Anyone who remembers the reunification of the city in 1967, how healing it felt when the wound of a boundary was removed from the city’s heart, will understand immediately that it’s intolerable to contemplate a return to anything like status quo ante.

For some years, easy access between Jewish Jerusalem and Arab Jerusalem was experienced as liberation; it became routine. And then it became, and is, uneasy, as the blight of a security wall so brutally reminds us.

Yet plainly, in any final status arrangement, Israel will justifiably require that it have control over who enters its sovereign territory. Where and how shall that control be exercised?

And, while we’re talking Jerusalem, what about the Temple Mount? Is it really possible to imagine an area, unlike any other in the world, over which no nation has sovereign claim? Perhaps it is — but again, no quick slam-dunk.

And water, and air space, and details that niggle constantly at those who must go beyond the simple slogan, “two states for two peoples,” and come up with enduring arrangements.

Viewed in this manner, the very idea of partition seems dauntingly awkward, a point driven painfully home during a splendid symposium at Brandeis University the other day, convened on the occasion of the 60th anniversary of United Nations Resolution 181, which partitioned British-mandate Palestine. Opposition to a two-state solution is not always ideological, based on competing claims to the same land. It can be and sometimes claims to be simply pragmatic, a surrender to the idea’s complexity.

No one should imagine that the morning after a Palestinian state is established smiles will defeat the worry lines that now crease the brows of Palestinians and Israelis alike. Not the morning after, not the year after.

No, the logic of a two-state solution is not a utopian logic, not by a very long shot. Its logic is simply this: There is no alternative destiny that is less complicated.

Set to the side the fact that a unitary state means an end to Zionism’s offspring, the Jewish state. Believe that Zionism is obsolete, is no more than yet another god that failed, that nationalism is an anachronism, that a two-state solution is an idea whose time has passed, an impossible dream. What dream is then possible?

A secular democratic state liberal in philosophy and moderate in practice in which both peoples live amicably, nastiness and incitement outlawed, grudges and resentments buried underneath flower gardens? That is no dream, it is pure fantasy, a marriage not made in heaven but a product of the netherworld.

It would be fantasy even if it were governed exclusively by a college of elders — say, for example, made up by all the Nobel peace laureates. Or by the flower children’s children, or by Sean Penn, Angelina Jolie and Peter, Paul and Mary. Or by Harvard or any other professoriate.

That is why both Prime Minister Ehud Olmert and Foreign Minister Tzipi Livni spoke as forcefully on behalf of a two-state solution as they did in Annapolis — as, not incidentally, did Palestinian President Mahmoud Abbas.

Now comes the hard part, the part so filled with trip-wires. Already in Israel, the naysayers are shouting from the rooftops, and the admirable resolve that was on such vivid display in Annapolis seems to be receding.

The stakes, this time around, are enormous: Failure to move responsibly toward a two-state agreement would likely consign the idea to the ash heap of history, ensuring a future not less bloody than the past. That is a haunting specter; its implications should weigh heavily on the attitude of all those who hold Israel dear.