A consensus is gradually emerging in the United States that Washington and its allies must take whatever action is necessary to prevent Iran from becoming a nuclear power. Various options are advocated, from U.N.-mandated economic sanctions to airstrikes on suspected nuclear installations to active subversion of the mullah‐​controlled regime in Tehran.

All of these options are based on key assumptions about both the probable conduct of the Iranian government and the underlying political situation in Iran. Unfortunately, many of those assumptions are dubious at best.

A nuclear Iran would attack Israel. Advocates of a hardline policy toward Tehran argue that if Iran acquires nuclear weapons, it will use those weapons against Israel, its hated adversary. Fears of such a scenario have risen sharply in recent months following comments by Iran’s president that Israel should be wiped off the map.

Such a comment is certainly reprehensible, but does it negate the long‐​standing realities of deterrence? Israel has between 150 and 300 nuclear weapons of its own. Even if Iran does go forward with its nuclear program, it will not be able to build more than a dozen or so weapons over the next decade.

It would be suicidal for a country with a tiny nuclear arsenal to attack a county with a large arsenal. One should not confuse repulsiveness with suicidal tendencies. The current government of Iran is certainly repulsive, but it has never given evidence that it is suicidal. In all likelihood, rhetoric about wiping Israel off the map is merely ideological blather. Israel has more than a sufficient capability to deter an Iranian nuclear attack.

Iran would pass along nuclear weapons to terrorist groups. Tehran has a cozy relationship with a number of terrorist organizations in the Middle East, most notably Hezbollah. The pervasive assumption in the West is that if Iran obtains nuclear weapons, sooner or later it would pass one along to a terrorist ally.

But how likely is it that Iran would make such a transfer? At the very least, it would be an incredibly high‐​risk strategy. Even the most fanatical mullahs in Tehran realize that the United States would attack the probable supplier of such a weapon–and Iran would be at the top of Washington’s list of suspects.

Significantly, Iran has possessed chemical weapons for decades, yet there is no indication that it has passed on any of those weapons to Hezbollah or to Palestinian groups that Tehran supports politically. Why should one assume that the mullahs would be more reckless with nuclear weapons when the prospect of devastating retaliation for an attack would be even more likely? The more logical conclusion is that Iran, like other nuclear powers, would jealously guard its arsenal.

It would be easy to overthrow the mullahs. American proponents of regime change — most prominently Michael Ledeen of the American Enterprise Institute — insist that the current government in Tehran is ripe for overthrow. Indeed, advocates of regime change typically argue that an invasion of the country would be unnecessary; rather, American financial and political support for dissident groups, combined with destabilizing special forces operations, should be sufficient.

There is undoubtedly significant popular discontent with the dour and repressive mullahs, but it is easy to overestimate the extent and clout of the opposition. It is not reassuring that many of the loudest American enthusiasts for a strategy of regime change are the same people who argued that the Iraq mission would be brief and easy and that Ahmed Chalabi was the most popular politician in Iraq. Those predictions proved to be spectacularly wrong, and we therefore should be doubly cautious about following the advice of that faction regarding Iran.

A democratic Iran would renounce all nuclear ambitions. This is the favorite assumption of those Americans who believe that Washington should pursue an aggressive policy of regime change. They argue that Tehran’s nuclear program is merely the pet initiative of the Islamic elite, while the bulk of the Iranian people are indifferent or hostile. Regime change, therefore, would not only remove an odious regime, but also provide the ultimate solution to the nuclear problem.

It is yet another dubious assumption. Tehran’s nuclear ambitions date back to the Shah of Iran in the 1970s. The bulk of the evidence suggests that a “peaceful” nuclear program has widespread support in Iran for reasons of national pride and regional prestige. The goal of a nuclear‐​weapons arsenal is more controversial, but given the dangerous neighborhood in which Iran is located, support for that objective also goes well beyond the mullahs and their staunch allies. Washington could be making a serious miscalculation if it assumes that a democratic Iran would be content to remain non‐​nuclear.

The Iranian nuclear issue is a hellishly difficult problem, and the United States has no good policy options. But whatever course U.S. leaders ultimately adopt must at the very least be based on sound assumptions. Unfortunately, some of the most crucial assumptions appear to be anything but well founded.