Many people are understandably puzzled by the refusal to freeze settlement construction. Binyamin Netanyahu has offered no explanation and, at first glance, it seems utterly illogical. Why would Israel court confrontation with its only ally merely to increase the almost 300,000 settlers by, at most, another few thousand?

The answer, of course, is that those few thousand people are not the point. What is at stake here is a principle - reciprocity, meaning no concessions without getting something concrete in exchange. And bitter past experience with forgoing cash on the barrel is precisely why it is refusing to do so now.

That experience began with UN Security Council Resolution 242, the basis for every subsequent land-for-peace proposal. This resolution required Israel to withdraw from "territories" captured in the 1967 war - not "the territories" or "all the territories." According to the resolution's drafter, Britain's UN ambassador Lord Caradon, this wording was deliberately chosen to let Israel retain some captured territory, because the 1949 armistice lines were not defensible. As he later explained, "It would have been wrong to demand that Israel return to its positions of June 4, 1967, because those positions were undesirable and artificial."

Arthur Goldberg, then America's UN ambassador, concurred: "The notable omissions - which were not accidental - in regard to withdrawal are the words 'the' or 'all'... the resolution speaks of withdrawal... without defining the extent of withdrawal."

Israel accepted 242, believing that by agreeing to concede some land, it had gained international support for retaining other areas needed to create defensible borders. And in 1982, it in fact quit 90 percent of the territory captured in 1967. But the reciprocity quickly evaporated: Today, no country, including the US, acknowledges Israel's right to retain any territory. Only its obligations remain on the table.

FAST FORWARD to the 1993 Oslo Accord, under which Israel left most of Gaza plus six major West Bank cities, and promised further withdrawals, in exchange for Palestinian promises to end terror. Instead, Palestinians killed more Israelis in the next 30 months than during the entire preceding decade. Yet rather than pressing the Palestinians to fulfill their promises, the world demanded more Israeli concessions. And Israel caved in: It quit Hebron (1997), signed the Wye Agreement (1999) and finally offered the Palestinians more than 90 percent of the territories, including parts of Jerusalem, at Camp David in 2000. Thus it again discovered that its commitments are binding, but reciprocal commitments swiftly evaporate.

Two months after Camp David, the intifada began. Over the next five years, Palestinians killed more Israelis than during the entire preceding 52 years, using land ceded to them as bases. Since Bill Clinton, the Camp David mediator, had blamed the talks' failure on the Palestinians, and since Palestinians began the violence, Israel naturally expected the world to finally demand that the Palestinians honor their commitments.

Instead, the world again demanded more Israeli concessions (which it received, at Washington and Taba in 2000-2001), while condemning every effort at self-defense, from checkpoints to arrests to targeted killings. Moreover, the country's international standing plummeted: In one 2003 poll, for instance, Europeans termed it the number one threat to world peace. Hence the promised recompense for the Camp David concessions, international support, again disappeared the moment it was needed. But the concessions remained, becoming the mandatory starting point for all subsequent talks.

Next came the disengagement. In 2005, 25 settlements in Gaza and the West Bank were uprooted and the IDF left Gaza. In exchange, Jerusalem was promised both international support and the reinstatement, via George W. Bush's letter of April 2004, of America's broken 1967 pledge to support adjustments to the 1949 lines.

But again, both "payments" soon evaporated. When the disengagement produced daily rocket barrages from Gaza, the world responded by condemning Israel for its efforts at self-defense. It is Israel, not Hamas, that the UN is investigating for war crimes, and IDF officers, not Hamas leaders, who risk arrest in Europe.

Moreover, US President Barack Obama swiftly abrogated Bush's letter, as his demand for a total settlement freeze demonstrates: If he supported retention of certain settlements, there would be no reason to oppose construction within those settlements, as opposed to outside them.

IN SHORT, whenever Israel has made concrete concessions in exchange for promises, those promises have proved kited checks when it tried to cash them - leaving it worse off, in terms of both security and international relations, than it was before making these concessions. This bitter experience is precisely why Netanyahu, whose motto was "if they give, they'll get; if not, they won't," was elected. And a settlement freeze is a real concession. First, precisely because the world opposes adjustments to the 1949 lines, the only hope of keeping areas deemed important is by moving enough people there that uprooting them becomes impractical. In that sense, those few thousand extra settlers do matter.

Second, a freeze sends the message that even Israel deems these areas negotiable, and defensible borders are not a red line.

Finally, a freeze would spark traumatic confrontations with settlers. As the disengagement proved, Israel does not fear such confrontations if it expects some compensatory benefit. But no society would court such trauma for no benefit at all.

And Obama has offered no benefit, aside from empty rhetoric about how a freeze would "facilitate" pressure on Iran and Arab progress toward normalization. No specifics on what kind of pressure or progress, nor any guarantee that they will actually materialize.

If Obama offered something concrete - say, a public Arab pledge of specific normalization measures within a specified time, or a public Security Council pledge of specific action on Iran by a specified date - along with an understanding that the settlement freeze would end if these promises were broken, Netanyahu would almost certainly agree. But Obama has made no such proposal, and Israel has had enough of making concessions in exchange for empty promises.

Unfortunately, Netanyahu has not yet even tried to explain this to the world. One can only hope that he uses his speech on Sunday to finally do so.