The existential-threat approach argues that a nuclear Iran is a threat to the survival of the Jewish people. The leadership in Iran has been very clear about its call for the annihilation of the Jews. Adolf Hitler was also clear about his intent to exterminate the Jewish population of Europe, and once Hitler acquired the capability, he did what he said he would do.
According to the existential approach, just as Hitler acted on his words, Iran will, too. The phrase "never again" dictates that Israel strike Iran's nuclear facilities before it is too late for the Jews, even if it only delays the program.
Another nuclear-power approach contends that the Iranian nuclear program is a threat in the same manner as the Soviet Union's during the Cold War. The United States viewed the leadership in Moscow as deterrable by a threat to retaliate against a nuclear or conventional attack with a massive nuclear strike.
Essential to this approach is the assumption that leaders can calculate the extraordinary cost of a nuclear war and would only risk it in the event that the state's survival is at stake. A post-nuclear Iran, too, can be deterred from launching a nuclear attack by the threat of a nuclear retaliatory strike from the U.S./NATO or perhaps Israel.
A nuclear-deterrence policy would entail containment, diplomacy and the U.S./NATO extending its nuclear umbrella to Israel and the Gulf states.
The unique-case approach accepts most of the other nuclear-power approach, but with one important caveat: The leadership in Iran is not rational; it does not calculate cost in the same manner as Western leaders and it does not conform to Western values, beliefs, and mores about human life.
Due to either culture or religion or fanaticism, Iran's leaders are willing to make irrational decisions based on messianic martyrdom. Iran's leadership cannot be deterred and is willing to engage in a nuclear war even if it results in certain annihilation.
This approach calls for the U.S./NATO to destroy Iran's nuclear facilities rather than merely a preventive strike to set it back three to five years.
Each approach is fraught with risks. In the existential-threat approach, Israel will pay a very high price for attacking Iran's nuclear program, including retaliation from Iran and Hezbollah in Lebanon and the possibility of provoking a region-wide war and damaging relations with the U.S. and European allies. In the aftermath of an attack, Iran might redouble its nuclear program and bombing might only temporarily delay it.
The other nuclear-power approach risks being wrong about whether Iran can be deterred, and especially wrong about whether Iran will risk nuclear war by extending its nuclear umbrella to Hezbollah or other terrorist organizations. Moreover, containing Iran will require a long-term and resolute American commitment, and could alienate China and Russia.
Finally, in the unique-case approach, for the U.S./NATO to destroy Iran's program will require repeated strikes and perhaps even the introduction of ground troops.
Steven E. Lobell is a professor in the Department of Political Science, University of Utah. He has recently published two co-edited books, "The Challenge of Grand Strategy" (Cambridge University Press) and "Beyond Great Powers and Hegemons" (Stanford University Press).