By Nobel Peace Prize standards, this year’s award to the International Campaign to Abolish Nuclear Weapons, or ICAN, wasn’t that terrible. At least the prize didn’t go to an arch-terrorist or a Communist dictator. Nevertheless, 2017’s prize sees the Norwegian Committee maintain a long tradition of celebrating peddlers of peace fantasies.

For that is what ICAN’s dream of a world without nuclear weapons amounts to: a dream that, if ever realized, would gravely imperil world peace.

Saying so puts me at odds with the great and the good in world opinion, serious national-security practitioners like George Schultz and Henry Kissinger, and the leader of my Church, Pope Francis. But proponents of “nuclear-zero” have yet to overcome the major intellectual objections to their project. That is because nuclear-zero rests on several faulty assumptions about the conduct of nations in war and peace.

ICAN and its allies assume that if the great nuclear powers reduced, shelved, and eventually eliminated their arsenals, others would follow suit. Yet it is equally if not more likely that once powers like the U.S. disarmed, others, especially rogue states, would race to build up their own arsenals. As the former Turkish diplomat Sinan Ülgen noted in an astute 2014 essay in the Bulletin of the Atomic Scientists, “Economic theory indicates that members of a cartel become more likely to engage in cartel-busting behavior as the rewards for doing so increase and the penalties decrease.” Breaking the anti-nuclear rule would pay massive security dividends at relatively little cost in a nuclear-zero context. That is, unless all the other members of the cartel prove willing to use military action to stop the opportunistic states. Such a regime, Ülgen wrote, is inconceivable in the real world.

Nuclear-zero also ignores the counterproliferation purpose of maintaining a credible arsenal. One of the major reasons that America maintains a large nuclear deterrent is to dissuade other powers, especially allies, from developing their own strategic weapons. As former U.S. Undersecretary of Defense (and COMMENTARY contributor) Douglas Feith has argued, “If there are serious doubts about America’s arsenal, friends who have lived under our umbrella will do their own proliferation.” Efforts to reduce the size of the U.S. operational arsenal are therefore likely to trigger more, not less, proliferation.

Nuclear-zero proponents, moreover, imagine that fewer strategic weapons would make the outbreak of catastrophic armed conflict less likely. This overlooks the fact that, without the tremendous destructive power of nuclear weapons, states are more likely to initiate conventional warfare, more likely to take risks, and more likely to devote a greater share of their resources to defense spending than they currently do. As Ülgen noted, “Nuclear deterrence has worked. Even at the height of the Cold War’s ideological polarization, the world never witnessed the sort of large-scale wars that, in the absence of a nuclear deterrent, were fought in the first half of the 20th century.”

Groups like ICAN, then, are really in the business of pretending that it is possible to return the world to the pre-nuclear age. Aggressive, revanchist powers like China and Russia will never agree. Nor will rogues like North Korea and Iran. It is impossible to “un-invent” nuclear weapons, as Feith has said, and a superpower like the U.S. can’t afford to live by fantasy.