President Barack Obama lives in the kind of world that I’d love to live in. Everyone (except those Tea Partiers) is reasonable and considers first the common good for all humanity. No one seeks to enrich themselves at their neighbor’s expense. No one seeks revenge over ancient insults. No nation dominates another.

Unfortunately, this is not the real world.

President Obama would like to live in a world where there are no nuclear weapons.

So would I.

But serious adults know that this will never be possible. You can’t uninvent a weapon, you can only make it obsolete.

Obama’s new nuclear posture review breaks with decades of ambiguity on when we would use nuclear weapons and gives our enemies – at least for the next 2 1/2 years – some idea of what we will and won’t do.

It eliminates much of the ambiguity that has deliberately existed in American nuclear policy since the opening days of the cold war. For the first time, the United States is explicitly committing not to use nuclear weapons against nonnuclear states that are in compliance with the Nuclear Nonproliferation Treaty, even if they attacked the United States with biological or chemical weapons or launched a crippling cyberattack.

Those threats, Mr. Obama argued, could be deterred with “a series of graded options,” a combination of old and new conventional weapons. “I’m going to preserve all the tools that are necessary in order to make sure that the American people are safe and secure,” he said in the interview in the Oval Office.

Let’s think about this for a second: Does this make you feel safer? What’s the up-side for American security with this announcement?

Yes, the Nobel Peace Prize Committee gets a shiver up their leg. Unfortunately that’s not a positive.

Imagine you find yourself in the situation we find ourselves in today: We’re embroiled in two regional wars (while Iraq is relatively quiet, we still have some 90,000 troops there) and our military is if not over-extended, then at least at something resembling 100 percent employment.

Now imagine you’re someone like Hugo Chavez – an America-hating opportunist and you think there’s a chance you can hit the U.S. with a crippling biological or chemical attack. If the U.S. is eventually able to trace it back to you, how much can they do right now? You know you’re not going to get nuked, and maybe you can survive the cursory bombing campaign likely to follow long enough to topple a U.S. ally like Columbia.

Some argue that this really isn’t a big deal. I hope they’re right.

However, it never hurts to keep your enemy guessing.