Should the United States invade Iraq and depose Saddam Hussein? If the United States is already at war with Iraq when this article is published, the immediate cause is likely to be Saddam’s failure to comply with the new U.N. inspections regime to the Bush administration’s satisfaction. But this failure is not the real reason Saddam and the United States have been on a collision course over the past year.

The deeper root of the conflict is the U.S. position that Saddam must be toppled because he cannot be deterred from using weapons of mass destruction (WMD). Advocates of preventive war use numerous arguments to make their case, but their trump card is the charge that Saddam’s past behavior proves he is too reckless, relentless, and aggressive to be allowed to possess WMD, especially nuclear weapons. They sometimes admit that war against Iraq might be costly, might lead to a lengthy U.S. occupation, and might complicate U.S. relations with other countries. But these concerns are eclipsed by the belief that the combination of Saddam plus nuclear weapons is too dangerous to accept. For that reason alone, he has to go.

Even many opponents of preventive war seem to agree deterrence will not work in Iraq. Instead of invading Iraq and overthrowing the regime, however, these moderates favor using the threat of war to compel Saddam to permit new weapons inspections. Their hope is that inspections will eliminate any hidden WMD stockpiles and production facilities and ensure Saddam cannot acquire any of these deadly weapons. Thus, both the hard-line preventive-war advocates and the more...