You can’t put the Genie back in the bottle. The twentieth century brought about a weapon of such magnitude that we now, for the first time in the history of our existence as a species, have the power to utterly destroy our entire planet. I’m not talking about fossil fuels, though their use ranks with many as a greater danger, but rather nuclear technology.
Of course, like many things, nuclear technology is in-and-of itself neutral. It can be used for good, providing clean energy to the entire world (solving Al Gore’s problem). It can also be used for evil, the creation and use of weapons with enough power to make the mind boggle. The United States is the only country in the world ever to have used nuclear weapons in war, and we have only done it twice during a single conflict (World War II). Thankfully, the nuclear powers of the world have thus far used discretion.
I can accept the existence our nuclear arsenal, since we are extremely unlikely to ever use it except in response to somebody else using nuclear weapons on us. I don’t mind Israel, for example, having nuclear weapons either, since they are clearly only going to use them as deterrent and defensive weapons. I’m a little more wary of Russia, China, India, and Pakistan having them, but I’m not too worried since their leaders have shown enough sense not to commit suicide (the doctrine of ‘Mutually Assured Destruction‘ is, indeed, still alive). India, Pakistan, and Russia are, at least nominally, democracies like Israel, the United States, and the nuclear-capable European powers. China is non-democratic, but its leaders for the last several decades have limited themselves to only committing evil acts against its own citizens.