AMBRIDGE, Mass., Sept. 20 — Harvard University's president, Lawrence H. Summers, used a quiet prayer meeting on the first day of classes here this week to condemn what he termed growing anti-Semitism at Harvard and elsewhere.
But while he labeled his remarks unofficial, they are setting off ripples on this campus, where students and professors have demanded that Harvard remove all Israeli investments from its endowment.
While Mr. Summers has drawn praise in some quarters for taking a stand, some in the academic community accused him of shutting off discussion.
"We are essentially being told there can be no debate," said John Assad, an assistant professor of neurobiology at Harvard medical school who signed the Harvard divestment petition. "This is the ugliest statement imaginable to paint critics as anti-Semitic."
Others, however, praised Mr. Summers for stepping into the debate.
"His remarks were very important," said Abraham H. Foxman, national director of the Anti-Defamation League. "What's frightening is that we've been seeing the rise in anti-Semitism again, and there are so few people willing to stand up and say anything."
Mr. Summers, who described himself in his speech as "Jewish, identified but hardly devout," declined to comment today, saying he wanted his remarks to stand on their own.
In his morning prayer address on Tuesday in Memorial Church, Mr. Summers said he saw anti-Semitic actions on the rise in academic communities around the world.
"Serious and thoughtful people are advocating and taking actions that are anti-Semitic in their effect if not their intent," said Mr. Summers, referring both to the push for divestment and to actions by student organizations at Harvard and other campuses to raise money for groups found to have ties to terrorist groups.
"Where anti-Semitism and views that are profoundly anti-Israeli have traditionally been the primary preserve of poorly educated right-wing populists," he added, "profoundly anti-Israel views are increasingly finding support in progressive intellectual communities."
His speech, which was reported first in The Harvard Crimson, is posted on Mr. Summers's Web site, president.harvard.edu/speeches.
Mr. Summers is known for his outspokenness. In the last year, he has been in a public dispute with members of Harvard's Afro-American studies department. One professor, Cornel West, left Harvard for Princeton after Mr. Summers urged him to serve as a leader in tamping down grade inflation and encouraged him to focus more on his scholarly work.
Mr. Summers said on Tuesday that he was making his remarks "not as president of the university but as a concerned member of our community."
But Taha Abdul-Basser, a graduate student in the department of Near Eastern languages and civilization and a member of the Harvard Islamic Society, questioned whether it was possible to separate the statements from the office.
"I understood his comment that he wished to be understood as an individual speaking, rather than as president, but I doubt that everyone who listened to the speech or read it will be able to make that distinction," Mr. Abdul-Basser said. "And I was saddened to see that evidently support of the divestment campaign was being equated with something as ugly as anti-Semitism. Some of the professors who supported the campaign said they saw a difference between the two, and I certainly do, too."
While Mr. Summers strongly rejected divestment, he affirmed the value of open debate and said he was not taking sides.
"There is much to be debated about the Middle East and much in Israel's foreign and defense policy that can be and should be vigorously challenged," he said in his speech.
Those caveats, however, did not persuade critics like Elizabeth Spelke, a psychology professor who also signed the divestiture petition.
"Labeling the petition anti-Semitic is a strategy to detract from the criticisms of Israel," Professor Spelke said. "It turns the substance of a political debate into a debate of morals and supposed racism."
But Eli Sprecher, a Harvard sophomore, said he welcomed Mr. Summers's willingness to speak out, saying: "He's not just the president of a university, he's the president of Harvard. If there's a pretty big issue, he should take a stand on it."
Mr. Sprecher said that Mr. Summers had made valid points about the divestment movement and that "comparing Israel to apartheid South Africa does border on anti-Semitism."
Lawrence S. Bacow, president of nearby Tufts University, applauded Mr. Summers for his stand. "University presidents ought to raise important questions and I think he has," Mr. Bacow said, adding that he, too, was concerned about signs suggesting a rise in anti-Semitism on campuses.
Earlier this year, nearly 600 professors, students, staff members and alumni from Harvard and the Massachusetts Institute of Technology, signed a petition urging Harvard and M.I.T. to divest from Israel. Similar efforts have been mounted at about 40 other universities.
The Harvard/M.I.T. petition said that "universities ought to use their influence — political and financial — to encourage the United States government and the government of Israel to respect the human rights of the Palestinians" by divesting from Israel and from American companies that sell arms to Israel.
Others at Harvard and M.I.T. fought back with a petition opposing divestment.
In May, Mr. Summers declared that Harvard had "no intention" of divesting, adding, "Harvard is first and foremost a center of learning, not an institutional organ for advocacy on such a complex and controversial international conflict."
In his remarks this week, Mr. Summers noted that his family had left Europe at the beginning of the 20th century. He said that for him, the Holocaust was "a matter of history, not personal memory" and that anti-Semitism "has been remote from my experience."
Mr. Summers, who became Harvard's president in July 2001, concluded his speech by saying he hoped he was wrong in his assessment of a rise in anti-Semitism and also hoped that it proved "to be a self-denying prophecy — a prediction that carries the seeds of its own falsification."
"But," he concluded, "this depends on all of us."