Despite repeated setbacks, Mr. Cohen’s broad recipe for peace in the troubled region remained remarkably consistent, according to “The Go-Between,” a memoir he published last year (written with Oren Rawls), as well as other accounts.

He generally favored the gradual emergence of a United Nations-mandated Palestinian state supervised by the United States and the North Atlantic Treaty Organization, though that, he wrote, would require “the gamble for peace by a great regional leader” and “the American refusal to take no for an answer.”

In an interview with the Times columnist Thomas L. Friedman in 2003, Mr. Cohen said: “Israel can’t force the Palestinians to be reasonable, to pursue their interests and not their passions, but it can create a context where they are more likely to do so than not. But with its relentless settlement activity, and responding to every Hamas provocation by smashing the Palestinian Authority, Israel has not done that.”

Meanwhile, Mr. Cohen said in 2002, “it turns out Arafat wanted two Palestinian states.”

“He wanted a Palestinian state for the West Bank and Gaza to be negotiated with Israel today,” he added. “And he wanted a Palestinian state inside Israel that would be brought about by a return of Palestinian refugees and their soaring birthrate tomorrow. Israel was ready to give him one Palestinian state, but not two. And Arafat didn’t have the courage to tell his people that.”

Stephen Philip Cohen was born in Quebec on May 28, 1945. His father, Harry, an immigrant from Lithuania, owned an auto parts business. His mother, born in Montreal to Jewish immigrants from Romania, was a bookkeeper.

He received a bachelor’s degree from McGill University in Montreal and a doctorate from Harvard. He was an assistant professor at Harvard, an associate professor at the City University Graduate Center and an analyst for the Israel Policy Forum, a Manhattan think tank that favors a two-state solution.

In 1973, after Egypt launched a surprise attack against Israel in what became known as the Yom Kippur War, Mr. Cohen took a leave from Harvard to enlist in the Israeli Army and use his training as a social psychologist to bolster morale at the front.