Demography denial is back in fashion. It's Israel's equivalent of climate-change denial. Faced with numbers that threaten their ideology, some politicians dismiss the statistics or invent new ones. Why let reality get in the way?

The numbers that upset demography deniers are population figures for the occupied territories. In fact, you can understand the Israeli political debate since 1967 as an argument between the Mathematics Front and the Alliance of Wishful Thinking. In the occupation's early years, the Math Front pointed out that the Palestinian birth rate was higher than the Jewish rate, and made projections of eventual Jewish-Arab parity between the river and the sea. Ergo, the only way for Israel to remain both a democracy and a Jewish state was to give up occupied land. Back then, Wishful Thinkers predicted that vast Jewish immigration would maintain a solid Jewish majority in the Whole Land of Israel, making withdrawal unnecessary.

In 1972, for instance, one of Labor's most prominent Wishful Thinkers, Shimon Peres, told his party's central committee that Israel should keep the West Bank, with confidence that Jews would immigrate in droves from the United States, Europe and the Soviet Union. Then-finance minister Pinhas Sapir, speaking in defense of arithmetic and democracy, explained that birth rates and compound interest worked the same way. By Israel's 50^th birthday in 1998, he said, 48.5 percent of the people between the river and the sea would be Arabs. Even with massive Jewish immigration, he said, Arabs would be over 40 percent of the Whole Land's population. (In 1998, after the mass immigration of ex-Soviet Jews, about 44 percent of the people between the Jordan and Mediterranean were Arabs.) Warning of the moral price, Sapir demanded, "Is this the Jewish state we aspired to?"

With time and population growth, you didn't need to be able to do compound interest; you just had to be able to count. Peres started sounding more like the late Sapir. Likud aristocrats, children of Irgun fighters, looked at the numbers and gave up on the Whole Land. Ehud Olmert came around in 2003 as Israeli and Palestinian Authority government statistics showed impending Jewish-Palestinian parity.

Since then, the Alliance of Wishful Thinking has resorted to shrinking the number of Palestinians. A 2006 report, "The Million Person Gap," charged that the Palestinian Central Bureau of Statistics (PCBS) had over-counted in its 1997 census and then projected too high a growth rate for subsequent years. The report said 1.4 million Palestinians lived in the West Bank, a million less than the PCBS said. In Gaza, it asserted, the PCBS had over-counted by 300,000. Leading Israeli demographer Arnon Sofer said "The Million Person Gap" included "deliberate deceptions" and "showed contempt for the Israeli public."

When a new census in 2007 found 2.35 million Palestinians in the West Bank, prominent demography denier Yoram Ettinger claimed that the PCBS had inflated its numbers by 50 percent. Leaving out Gaza, he asserted, Jews were a solid 67 percent majority between the river and the sea.

In recent weeks, the Wishful Thinkers are out in force. In an op-ed article, Likud elder and ex-defense minister Moshe Arens pretended there was no census, just unreliable predictions that couldn't justify "cutting the heart out of the Land of Israel." Reporting on Deputy Transportation Minister Tzipi Hotovely's proposal that Israel annex "Judea and Samaria," settler news site Arutz Sheva explained that "estimates" of the Palestinian population "vary from 1.5 to 2.4 million." Jewish Home leader Naftali Bennett gave the lower number as fact in his Washington Post interview. The paper didn't challenge his figures.

Reality check: In a document just published by Haaretz, Israel's Civil Administration listed over 2.6 million Palestinians living in the West Bank as of May last year, not counting East Jerusalem. Adjusting for the fact that Civil Administration doesn't deal with East Jerusalem, the figure is a tad higher than the PCBS's current estimate.

But the fundamental issue isn't demography. It's the mathematics of democracy. Accept the Wishful Thinkers' numbers for a moment; even force yourself to forget about Gaza. Will Israel continue to rule over 1.5 million West Bank Palestinians who can't vote in Israel? Or will it give them citizenship, and end up with a parliament that—per the wishful statistics—will have about 80 Jewish and 40 Arab members? The Wishful Thinkers belong to the political camp that most strongly opposes including Arab parties in a ruling coalition, the camp that assailed the late Yitzhak Rabin's legitimacy because his government depended on Arab votes. Will the Wishful Thinkers change their minds post-annexation? Or will they expect a prime minister to win the support of 61 out of 80 Jewish members of parliament? The lifetime of such a coalition—if formed at all—would be measured in days, not months.

I can't tell you which of the demography deniers are fooling themselves, and which are trying to con the rest of us. Either way, their argument for continuing to rule the West Bank just doesn't add up.