When I was in elementary school in the early 1960s, we were periodically put through “duck and cover” drills under the risibly ridiculous fantasy that our flimsy wooden desks would protect us from a thermonuclear detonation over Los Angeles. When I was an undergraduate at Pepperdine University in 1974, the father of the hydrogen bomb, Edward Teller, spoke at our campus about the effectiveness of mutual assured destruction (MAD) to deter war. He said that by stockpiling many weapons neither side has anything to gain by initiating a first strike because of the retaliatory capability of both to send the other back to the Paleolithic.

So far MAD has worked. But as Eric Schlosser reveals in his riveting 2013 book Command and Control, there have been dozens of close calls, from the Cuban missile crisis to the Titan II missile explosion in Damascus, Ark. And popular films such as Stanley Kubrick's 1964 Dr. Strangelove have played out how it could all go terribly wrong, as when General Jack D. Ripper becomes unhinged at the thought of a “Communist conspiracy to sap and impurify all of our precious bodily fluids” and orders a nuclear first strike against the Soviet Union.

A deterrence strategy like MAD is not a long-term sustainable solution because of escalation, accidents and crazies, and efforts have been made over the past two decades to reduce the world's stockpiles, from a peak of around 70,000 in 1986 to about 17,300 today, only 4,200 of which are operationally active nuclear warheads. Can we get to “nuclear zero”?

The original cold warrior himself, Ronald Reagan, thought we could. He considered nuclear weapons to be “totally irrational, totally inhumane, good for nothing but killing, possibly destructive of life on earth and civilization.” Also calling for “a world free of nuclear weapons” are such cold warriors as former secretaries of state Henry Kissinger and George Shultz, former secretary of defense William Perry and former senator Sam Nunn of Georgia in, of all places, the Wall Street Journal. The movement Global Zero has charted a path to reach that goal by 2030. General James E. Cartwright, formerly vice chairman of the Joint Chiefs of Staff, says that the U.S. and Russia could reduce their nuclear arsenals to 900 weapons each and still maintain a deterrence peace until, later, they reach zero through diplomatic means. It's worth noting that 185 of the world's 194 countries (95 percent) are doing just fine without nuclear weapons, and more nations have started and abandoned nuclear weapons programs than started and completed them. This is encouraging, but is it fail-safe?

To find out, I audited a class called Perspectives on War and Peace at Claremont Graduate University, taught by political scientist Jacek Kugler. His answer is no, for these reasons: One, some states that have nukes, such as North Korea, are unpredictable. Two, rogue states want nukes. Three, states waging conventional wars might escalate to using nukes. Four, if terrorists get nukes, they'll use them. Five, the taboo against using nuclear weapons has not yet expanded into a taboo against owning them, and so the danger of accidents or unhinged leaders remains. And six, the nuclear genie of how to make an atomic bomb is out of the bottle, which means other nations or terrorists can obtain them and destabilize deterrence.

Kugler thinks we can have “regional zero”—nuclear-free zones such as Latin America and Australia—provided the largest nuclear powers (the U.S., Russia, China and the European Union) agree to provide a secure response, which none can veto, to any preemptive use of nuclear weapons by rogue states. Even then, nonstate entities such as terrorist groups may be able to purchase fissile material on the black market, and if they do there is nothing to deter them because many look forward to a martyr's death.

With the ongoing terrorist threat and the lack of trust between nuclear nations (Russia comes to mind), nuclear zero is not yet in the cards. But if we continue to reduce the size of the global stockpile, reinforce the “no first use” policy, amp up the taboo against owning nukes, guard all fissile material, increase economic interdependency and spread democracy, we can inch our way to global security.