By Fareed Zakaria
Thursday, August 6, 2015

Many critics of the nuclear deal with Iran believe that the problem lies in the disposition of the president. “A very, very naive man who does not know how the world works,” said Rick Perry of President Obama. “Dangerously naive,” noted Lindsey Graham. In fact, Obama is not naive, but disposition does matter. Obama is an optimist — about the world, the United States’ place in it and even the threats it faces in the Middle East. And history suggests that it’s the optimists who have tended to be right.

Today we are awash in pessimism, with people who see the world as a dark and dangerous place, where threats are growing and enemies are gaining strength. Last year, John McCain declared that the world is “in greater turmoil than at any time in my lifetime” (which includes the rise of fascism, Nazism…