In trying to plan for the future, world leaders are looking to the past. “When this crisis is over, there has to be a vision of what comes next, and in our view it has to be a two-state solution,” said Joe Biden, America’s president, in one of his many public statements about the nearly month-long war in Gaza. Rishi Sunak, the British prime minister, has made similar comments; so has Emmanuel Macron, the French president. An emergency meeting of the Arab League last month ended with a call for “serious negotiations” towards a two-state solution.