Many critics of the nuclear deal with Iran believe that the problem lies in the very disposition of the president. “A very, very naive man who does not know how the world works,” says Rick Perry. “Dangerously naive,” notes Lindsey Graham. In fact, Barack Obama is not naive, but disposition does matter. Obama is an optimist – about the world, America’s 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. In 2014, John McCain declared the world is “in greater turmoil than at any time in my lifetime” (which includes the rise of fascism, Nazism, World War II and the Soviet nuclear threat). We’ve seen this before, often. In an essay in 1989, Harvard scholar Samuel Huntington noted that the United States was experiencing its fifth wave of this kind of pessimism since the 1950s.

First, he explained, Sputnik shocked America, and by the early 1960s, the country was convinced that the Soviet Union was on a path to overtake it economically, technologically and militarily. In the late 1960s and early 1970s, as Vietnam sapped the nation’s confidence, the Nixon administration urged Americans to get used to a multipolar world with a diminished place for Washington. When the oil shocks of the 1970s hit, people saw the Middle East’s petro-states as the world’s new power brokers. By end of the 1970s, with the Soviet Union modernizing its nuclear arsenal and on the march – from Afghanistan to Central America – scores of commentators prophesied that Moscow was winning the Cold War. And when Huntington wrote his essay, it was conventional wisdom that an invincible Japan would soon become the world’s No. 1 economic power.

Of course, not one of these fears proved to be valid. There was a kernel of truth in each of them – an event or trend that deserved to be countered or responded to. But the dark view almost always led to a vast overestimation of our adversaries’ power and strategic capabilities. The missile gap with the Soviet Union was nonexistent, the oil rich states proved dysfunctional, the Soviet Union’s interventions in Afghanistan marked the beginning of the end for that superpower, and Japan’s much-vaunted economic model collapsed just as we were panicking about it.

I would update Huntington’s list to add the fears that have bubbled up since 9/11 – that radical Islam is an existential danger and that Americans are defenseless against it, that Saddam Hussein’s Iraq posed an intolerable danger to America, and, now, that an “imperial” Iran is poised to dominate the Middle East.

In his speech at American University this week, Obama tried to place Iran in context. It is a middling regional power with some limited ambitions and capacity. As he pointed out, its Gulf foes outspend it militarily by eight to one. America outspends it by 40 to one. Tehran is desperately trying to prop up Bashar Assad’s regime in Syria. This is an expensive strategy that is unlikely to work in the long run since Assad’s group, the Alawites, represent less than 15 percent of the country. Meanwhile, Iran is also fielding forces in Iraq to fight the new, rising threat from ISIS, which is above all an anti-Shiite terror group. Being forced to fight on two fronts to preserve your security is not a sign of strength.

Think of the mistakes the United States has made when it acted out of fear, convinced that its enemies were 10 feet tall and about to triumph. In the 1950s, it helped depose democratic leaders in the Third World, fearful that they would become socialists. Later, it intervened in Vietnam. It supported the apartheid regime in South Africa. It invaded Iraq.

On the other hand, when we have kept threats in perspective and understood that time was on our side, we have patiently organized our allies, negotiated agreements with our adversaries, built our internal strength and, in the end, prevailed. It is not as satisfying as the imagined thrill of military victory, but it has been a much surer path to stability and success.

Look at the facts. The United States has outlasted monarchy, fascism, revolution and communism. It will handle the threat from a middling regional power like Iran. It will outlast radical Islam, an ideology that has no answers for the modern age. To recognize this is not naiveté but confidence, a confidence in America that is confirmed by history.