Renowned physicist Stephen Hawking has canceled his planned appearance at next month's Presidential Conference in Jerusalem, apparently in response to the urging of Palestinian activists and academics.

Hawking informed President Shimon Peres of his decision last weekend, but decided not to make it public. Thus it became public knowledge only yesterday, when it was reported on the website of the British Committee for the Universities of Palestine and picked up by the British daily The Guardian.

According to the statement published with Hawking's approval by BRICUP, a group that works to promote an academic boycott of Israel, the cancelation was "his independent decision to respect the boycott, based upon his knowledge of Palestine, and on the unanimous advice of his own academic contacts there." The group didn't publish Hawking's letter to Peres, but said it would do so if it received his permission.

Later, Cambridge University, where Hawking is a professor emeritus, said the 71-year-old physicist had canceled because of health problems, and that he had not confirmed BRICUP's statement. Hawking suffers from a motor neuron disease that has left him almost entirely paralyzed. But the university subsequently issued a retraction, saying that Hawking's office had confirmed the statement. Hawking has been in Israel several times before, most recently in 2006.

But in the four weeks since his attendance at the conference, called "Facing Tomorrow," was announced, he has come under heavy pressure from activists who favor an academic boycott of Israel, both within Britain and outside it. Finally, Hawking told friends he had decided to listen to his Palestinian colleagues and stay home.

Conference chairman Israel Maimon told the Guardian that Hawking's decision was "outrageous and wrong."

"The use of an academic boycott against Israel is outrageous and improper, particularly for those to whom the spirit of liberty is the basis of the human and academic mission," he continued. "Israel is a democracy in which everyone can express their opinion, whatever it may be. A boycott decision is incompatible with open democratic discourse."

In a subsequent conversation with Haaretz, Maimon noted that Hawking was being more Palestinian than the Palestinians: While he was boycotting the conference, other Palestinians had agreed to attend it as speakers.

"Hawking's stance strengthens the extremists," Maimon added. "After all, extremists don't talk; moderates talk. This boycott isn't a path that encourages dialogue, it only encourages the extremists."

The three-day conference, which will open on June 18 at Jerusalem's International Convention Center (Binyanei Ha'uma), is being cosponsored by the Hebrew University of Jerusalem. It will bring together people from the fields of government, economics, technology, science and entertainment to discuss the question of how to shape a better future for the world, the Jewish people and Israel.

Among the guests who have confirmed their attendance are singer and actress Barbra Streisand, who will sing at the opening event in honor of Peres' 90th birthday; former U.S. President Bill Clinton; former President of the Soviet Union Mikhail Gorbachev; actress Sharon Stone; Prince Albert of Monaco; Daniel Kahneman, winner of the 2002 Nobel Prize in economics; and a number of senior executives from the high-tech world.

Though Hawking's cancelation will surely be chalked up as a victory by proponents of an academic boycott on Israel, local academics say the boycott movement hasn't been very effective so far, and they see no signs of that changing.

"The boycott isn't progressing," said Prof. Asher Cohen, rector of Hebrew University. "Every so often there are local successes, like the Hawking case. But if you look at Europe, which is the bastion of the academic boycott it has the most prestigious scientific foundation, the ERC, which every country is competing [to get money] from. The Hebrew University is in fifth or sixth place in terms of the number of ERC grants it has received. That's important, because the decisions on these funds are made by Europeans. With competitive foundations of this sort, it's enough for one person to vote against, and you won't get the grant. From this standpoint, it seems the boycott is ineffective."

Dr. Anat Matar of Tel Aviv University concurred. Even in Hawking's case, she said, his cancelation should be seen "primarily as opposition to a propaganda wall masquerading as an academic event. In my view, there's no reason to attack Hawking over this as someone who's coming out against academic freedom. This is a conference with the president; it's public relations for Israel. It's not clear how Hawking would have chosen had he been invited to a conference of physicists."