A claim is making the rounds these days that since the two-state solution is unrealistic because of each side's positions and actions, Israel has no reason to declare its official support for the plan.

In response, the left increasingly promises that the Palestinians would be prepared for peace with Israel if only they were sincerely offered a viable state. The problem is that the other side does not always cooperate with this claim. For example, former Gaza strongman Mohammed Dahlan recently accused Hamas of slandering Fatah by claiming the latter is demanding that Hamas recognize Israel.

"This is a big lie," said Dahlan. "I am telling you for the thousandth time that we are not demanding that Hamas recognize Israel's right to exist. We demand that Hamas not do it, as Fatah itself has never recognized Israel's right to exist. We admit the PLO recognized Israel's right to exist, but that does not obligate us [Fatah] as a resistance movement."

The response on the left to such statements is to ignore them, or to try to explain them away. But the public is unwilling to ignore such statements, and the justifications have only destroyed the Israeli peace camp's credibility. It is not at all important whether Dahlan's words were sincere, or what were the precise tactical reasons he said them now. What is important is that he feels the need to make such a statement when he is competing with Hamas for the Palestinian public's support.

Fifteen years after Oslo, the Palestinian people are split into two camps: Hamas, which is not willing to make peace with Israel, and Fatah, about which we can say at most that it is unclear whether it is willing or able to reach a peace agreement and keep it.

So why should Israel declare its support for a two-state solution? The immediate, and less important, reason is the politicaldiplomatic one. Israel has to have a reasonable proposal for a solution, even assuming that there is no real chance of implementing it now. Otherwise, even our friends will blame us for continuing the conflict. It is impossible to control most of the West Bank and refuse to present a fair proposal for ending the occupation without being accused that all our claims against the other side are nothing but excuses, and that Israel is afraid of an agreement because it is not willing to pay the price.

When the right is in the opposition, it pretends that it is possible to ignore diplomatic constraints. When it is in power, the right accuses its own prime minister - every single one - of betraying his principles. That is a justifiable accusation; the right's principles are such that it is impossible not to betray them.

The deeper reason it is necessary to support the two-state solution is that it is a vital strategic interest for Israel. The only alternative to dividing the land is creating a single state from the Mediterranean to the Jordan River. Whether that happens sooner or later, it is clear that such a state would not be Jewish, and it would not be binational either. A state with an Arab majority in the middle of the Arab-Muslim Middle East would be an Arab state in every way.

The principle of two states for two peoples has another advantage: It is just. Its supporters can benefit from this advantage on the condition that they tell themselves and the Israeli public the truth, even when it isn't easy.