[B]oth theory and history teach us that getting a nuclear weapon has less impact on a country's power and influence than many believe, and the slow spread of nuclear weapons has only modest effects on global and regional politics. Nuclear weapons are good for deterring direct attacks on one's homeland, and they induce greater caution in the minds of national leaders of all kinds. What they don't do is turn weak states into great powers, they are useless as tools of blackmail, and they cost a lot of money. They also lead other states to worry more about one's intentions and to band together for self-protection. For these reasons, most potential nuclear states have concluded that getting the bomb isn't worth it.
But a few states-and usually those who are worried about being attacked-decide to go ahead. The good news is that when they do, it has remarkably little impact on world affairs.
I'll add that I would prefer that Iran not develop/obtain nuclear weapons because a not-strongly financed nuclear program can be dangerous. I mean dangerous in a meltdown sense, not the bombing other countries sense. Better to not create that risk than to have to worry about it, however small that risk may be. But I don't support basically starving the people of Iran in order to achieve the goal of deterrence. We need to find a better way.