Juan Cole argues that Iran isn't pursing a nuclear bomb, just nuclear latency:
Those who insist that Iran is trying to get a bomb have a difficult time explaining why Khamenei forbids it as un-Islamic and why the president and others all deny it. It is possible that they are lying, but their denials at least have to be noted and analyzed. The skeptics also have to explain away why the 16 US intelligence agencies say after exhaustive espionage and investigation that there is no weapons program now and that there hasn't been one for some time.
Before the Iraq fiasco, I would have dismissed this as naive hooey. I still suspect it is. But anyone not open to debate on the basic thesis has not learned from history. His hypothesis:
Those who agree with the CIA and the Defense Intelligence Agency, as well as with the International Atomic Energy Agency, that there is no evidence for Iran having a nuclear weapons program have to explain Iran's insistence on closing the fuel cycle and being able to enrich uranium itself.
The answer I propose, which explains all the anomalies elegantly and concisely, is that Iran is seeking nuclear latency. Latency is the possession of a nuclear energy program and of reactors, which would allow the production of an atomic bomb on short notice if an extreme danger to national autonomy reared its ugly head. Nuclear latency is sometimes called the 'Japan option,' because given its sophisticated scientific establishment and enormous economy, Japan could clearly produce a nuclear weapon on short notice if its government decided to mount a crash program.
This is surely the smartest move Tehran can make. It doesn't cross the trip-wire of international sanctions; it bolsters national pride; yet it does act as an implicit guarantee if it is attacked. And it could then be used, if inspections are allowed, to highlight Israel's nuclear monopoly in the region, and engender wider support for Israel to live up to the NPT. Quite shrewd actually. But we need a through inspection regime and full engagement with the coup leaders to find out.