Dan Drezner asks his "realist colleagues" if they can think of any reason why Iran should or would give up its nuclear ambitions. Stephen Walt offers some reasons why, unlikely as it might seem, Iran should consider doing so for its own advantage. I think Walt makes some good points but that they may not seem quite so persuasive when viewed from Tehran. In the end, too much of his argument is based upon the notion that the United States is Really Crazy, which risks leaving Walt making an argument that is the mirror image of the Mad Mullahs are Mad and Cannot Be Trusted Not to Do Mad Things line that often surfaces when Iran is the topic for discussion.
The biggest danger posed by a nuclear Iran is not the threat to Israel, but that it will lead to a further bout of regional proliferation. The mre nukes there are the greater the probability that someday the kooks will get their hands on one of them. But what about Israel? At the moment President Ahmadinejad's rhetoric is cheap and easy. Since Iran doe not have the ability to "wipe" Israel from the face of the earth it is easy to propose doing just that. Not that Ahmadinejad controls nuclear or military policy anyway. But once Iran has - as it probably will some day - a nuclear capability such rhetoric becomes riskier. It could have consequences in ways that it does not now.
As I say, we're often encouraged to think that the Iranian regime - exceedingly nasty though it is - cannot be trusted to act sensibly and that, consequently, it cannot be "allowed" to become a nuclear power. Ignoring the fact that this is not a permission slip that's actually in the American president's gift, this notion supposes that the Iranians are somehow uniquely blind to logic. Yet nothing in their current or recent behaviour supports this. Yes, they have acted in a provocative manne, not just in Iraq but in their support for Hizbollah. Yet there's been logic too: each Iranian provocation has been grave enough to make others consider military action but not sufficiently brazen as to justify it. That is, the Iranians seem to know how much and how far they may tease the American tiger. Perhaps this would change if they were a nuclear power, but there's no cmpelling evidence that I've seen to support that notion.
So the idea that Iran will build a bomb and drop it on Israel seems far-fetched. Yes there's that line about how you only need one bomb to eliminate Israel but many more to destroy Iran. When push comes to shove, however, few people find the certainty of nuclear annihilation all that attractive. That is, once again, the stakes are raised when such a prospect could actually happen. Paradoxically, then, the higher the stakes the safer we may. When a single miscalculation can have such fatal consequences the calculations tend to be checked pretty thoroughly. Then again, it's obviously a big risk: but since the Iranians haven't shown signs of terminal stpuidity so far, why should we suppose they will lose their minds when they have the bomb?
And as for the United States, well it might even gain something from an Iranian nuke. The Iranians may be paranoid but then they have reason to be. The US would like to see regime change in Tehran after all. But since the Iranians also, I think, crave respect and, in the end, some form of international rehabilitation, then the prospect of a nuclear Iran permits Persia to enagage with the rest of the world, and specifically the United States, from a position of some psychological strength. For its part, the United States retains, (I trust!) sufficient institutional memory as to be able to play th enuclear game with rather more finesse, subtlety and confidence than it has sometimes shown in more assymetric struggles. That is to say, the Iranians are experts at the latter kind of proxy conflict, while the Americans might be better suited to a return to a game of Nuke vs Nuke.
Now, in the end, I think it would be preferable if Iran didn't have nuclear weapons. But I suspect we're not really likely to be able to stop them from getting the bomb. That in turn leads one to suspect that we need to spend time thinking about how to live and deal with a nuclear Tehran.
UPDATE: James Fallows has more on this and related matters. As he says, an attack on Iran's nuclear facilities now would be stupid, self-defeating and wrong. Quite so.