Every analysis I have read about Iran's nuclear weapon program is based, I believe, on a mistaken assumption. We can best view this mistake by referring to analyses of a related issue, which is whether Israel is likely unilaterally and by itself to attack Iran's nuclear weapons production sites in an effort to destroy or set back the program. Analysts correctly state that that Israel's perspective on the issue is "existential"; that is, that for Israel, Israel's national existence, as well as existence of a significant portion of the world's Jews, who live in Israel, is at stake. Iran has consistently said it wishes to destroy the Jewish state and Jews along with it. Iran has stated this goal in credible terms.
When analysts turn to American-led efforts to compel Iran by sanctions to abandon its nuclear weapon's program, analysts explain Iran's program in practical - not existential - terms. They think Iran could abandon its program in order, e.g., to maintain certain international relations the sanctions curtail. The analysts do not speak of Iran as perceiving its nuclear weapons program as an existential issue for the Iranian state. That is a mistake. The Iranian state is the political manifestation of a religious regime in perpetual political and social revolution. By "revolution", I mean that the Muslim state sponsors continual change and alternation, in the name of a radical religious ideology, of the historical, social, political, and religious relations of its citizens and of Iranian relations with other states. That religious revolution is the essence of the state. It is also the source of existential enmity between Iran and its Muslim neighbors, Western democracies, and Israel.
Without the ongoing revolution, the Iranian state would transform into a static, administrative state, exposed to political reformism (evidence of which we saw in the recent Iranian reform uprising). For the Iranian state, the purpose of possession of a nuclear weapon is protect the existence of the revolution and the state that sponsors it. Possessing a nuclear arsenal would successfully deter other nations from attacking Iran, leaving the state free to perpetuate its revolution.
Iran and Israel have equal stakes in their horrific struggle. For both, the issue is existential. They are in a death struggle. This death struggle can only be ended by the complete destruction of Iran's nuclear weapons program and the transformation of the Iranian state. It would not end should Iran destroy Israel, for the revolution would be extended against other Muslim states and against democratic societies outself the Middle East, including the US. Military action must be taken, as soon as possible against the Iranian weapons sites.