If Iran develops nuclear weapons, would it use them against other countries? Is the danger so great that we should attack Iran now, as some in the White House are advocating?

A rational odds-maker taking bets on whether Iran would launch any nukes it gets would look at the history of nuclear weapons use.

Countries don't get nuclear weapons to use them. They get them to strengthen their bargaining power, and to protect themselves from others.

Remember "mutually assured destruction," the concept that kept the United States and the Soviet Union from launching against each other?

As between Iran and Israel, one of Iran's most discussed potential targets, the defensive rationale makes sense from Iran's point of view.

President Bush's inflammatory characterization of Iran an "axis of evil" country, combined with our general backing of Israel, has heightened Iran's concern about attack from Israel.

With Israeli nuclear warheads ready to be fired at Tehran, an Iranian nuclear capacity might make Israel think twice.

Nuclear weapons may seem to Iran a sensible way to keep Israel - and the United States - at bay. But what of Iran's belligerence and its threats toward Israel? Do they not suggest that Iran might strike Israel?

Iran hosted a conference recently that featured those who deny Nazi atrocities against the Jews in World War II. Iran's President Mahmoud Ahmadinejad has spoken of wiping Israel off the map.

Ahmadinejad commented on the Holocaust conference in his recent interview with ABC's Diane Sawyer. Without denying the Nazi atrocities, he said they do not justify what Israel does to the Palestinians.

If one listens closely to what Ahmadinejad says, the statements about Israel reflect criticism of Israel's practice and policies, not unlike criticism Israel gets from many quarters.

As to whether Israel should or should not exist, Ahmadinejad told Sawyer that the principle of self-determination should govern, and if the Palestinians and Israelis come to terms, that would be fine with Iran.

He said that the Palestinians - a term that he uses to include the Jews of Israel - should decide by referendum what kind of state or states to have.

Quite a few countries have nuclear weapons, but they don't launch. If Pakistan launches against India, India might launch back. And vice versa. Nuclear weapons are more useful unused.

French President Jacques Chirac, in a recent statement that outraged the White House, said that if Iran were to acquire nuclear weapons, it would not launch against Israel out of concern that Israel would strike back with the same.

Bush's protest made Chirac retract the statement, but its validity is hard to deny.

Another factor a rational bookie would consider is that the political situation in Iran may change, perhaps even before any nuclear weapons are developed.

The Iranian leadership faces strong sentiment from sectors of the Iranian population that fundamentalism and clerics should not govern. To many Iranians, an improved economy is more important than a high international profile.

When you put all this together, the chance that Iran would ever launch a nuclear weapon is slight. And the whole issue may blow over.

We were at odds with North Korea for more than a decade over its nuclear weapons, but the matter got resolved a few weeks ago in two days of meetings.

Nuclear weapons are better relegated to the scrapheap of history, to be sure. The world would be a better place without them.

There is no guarantee they will not be launched, perhaps accidentally. But the potential that Iran will build them, and after that the possibility that it might use them, provide no reason to go to war against Iran.

John B. Quigley is a professor of law at The Ohio State University. This commentary was distributed by McClatchy Newspapers.