I have an inherent faith in human beings; humans are essentially compassionate and want to be moral. Nevertheless, I believe that it is almost inevitable that nuclear weapons will be used again.
There is no contradiction. The answer lies in the second law of thermodynamics. Given the ocean of time ahead of us, the odds are very great that another Hiroshima and another Chernobyl will occur. It is the nature of our universe that powerful phenomena will constantly renew themselves, while the means to resist them do not.
Once, I saw a waiters' race in Washington, where the trick was to walk rapidly carrying a glass of water on a platter without spilling a drop. What are the odds that a given waiter will reach the finish line without a spill? What are the chances that every waiter will avoid spilling any water? Imagine that the race lasts a hundred, a thousand, or a hundred thousand years--what are the odds now? Now imagine that a single drop spilled kills a hundred thousand people, and an entire glass of water ends the human race. The longer the race lasts, the more jolts and jostles the waiters will experience, but they will not become any better at resisting them--in fact, over time they will get worse, because they are tired out or becoming older.
Even without malice or gross incompetence, it is inevitable that a glass will be spilled, and sooner, rather than later. It is in the nature of things; this inevitability sings to us from within the second law. Satellites do not rotate the Earth forever without experiencing hits from meteorites; the Earth does not rotate the Sun forever without getting hit by asteroids. Nothing lasts forever; tout casse, tout passe, tout lasse.
Any fate that depends on the will of the greatest number of people over the longest time is likely to be a happy one, because the majority of people are kind and good. But the proliferation of nuclear weaponry represents the ultimate tyranny of the minority; we are no longer relying on the good will of most people, but on all of them without exception, which means that we are relying on the good will of one man with his finger on the button.
When spears were first invented, some early sage certainly advocated that, between humans, they be used only for deterrence, and suggested, like Kenneth Waltz in The Spread of Nuclear Weapons, that they need never fly, so long as any potential aggressor knows that more spears will come flying back. At that same moment, another, more realistic sage, certainly thought: If it exists, it will be used. And when it happened--when an angrily or carelessly thrown spear first transfixed a human being--the result was the needless loss of one or a few lives. The atom bomb, by contrast, is the spear that ends the world when it is carelessly thrown.
Waltz appears to think that every single politician, every single military officer within reach of a nuclear weapon is a rational actor who will recognize that the terrible consequences outweigh any possible benefits. What Waltz fails to explain is: what in the nature of the universe dictates that not even one suicidal madman will ever control a nuclear weapon?
When the IRA tried to kill Margaret Thatcher, and missed, they sent her a message: "We only need to be lucky once. You need to be lucky every time." The bomb itself sends us the same message. Every nuclear weapon is a potentiality, a fission reaction suspended, waiting to occur. In the same sense that information wants to be free, or that water overflows its boundaries, every bomb is an explosion waiting to be let out. Potentialities happen and over a long enough spread of time, they inevitably happen.
Note that if I were saying that a rational government, unopposed, would inevitably use the bomb, I would then be arguing for deterrence. There is no way of deterring a mad or self-deluded human. Hitler was not deterred from launching a World War by the patent absurdity of the notion that Germany could fight the Soviet Union and the U.S. simultaneously.
Certain weapons of the past, such as poison gas, were deemed so horrible that they have all but passed from the Earth; so must the bomb. The madmen who would use it could not possess it if they could not obtain the technology from more major powers. If we stopped making bombs, we could not sell the technology and we would not be vulnerable to its theft. The most difficult task for humanity, and the ultimate test of our maturity, is the renunciation of a bad tool. There is no other way.