Once again people are getting spun up over elusive details about what a Middle Eastern regime is or is not doing regarding unconventional weapons. Participants in public debates over policy get seized with questions such as the significance of a soil sample or whether certain victims of Syria's civil war had dilated pupils. People wait with bated breath on whatever else intelligence can tell us about such things. It is as if the wisdom, or lack of it, of intervening in that civil war hinges on whether a particular regime has made use, however small, of a particular category of weapon. It doesn't.

Much has been said about avoiding mistakes that were made over a decade ago in leading up to the Iraq War. Certainly we should try to avoid repeating mistakes. But the biggest mistake that is being made now—and repeats a fundamental mistake in the public discourse prior to the Iraq War—is not an interpretation of evidence regarding somebody's unconventional weapons but instead is the false equating of an empirical question about weapons with the policy question of whether launching, or intervening in, a particular war makes sense.

Whether Saddam Hussein did or did not have WMD turned out to be one of the less important realities about the Iraq War. Even if everything that was said on this subject to sell the war turned out to be true, the human and material cost of the war would have been just as great (maybe even greater, if Saddam's forces had possessed and used such weapons), the post-Saddam political and security situation in Iraq would have been just as much of a mess, and launching the war still would have been a blunder.

In Syria today, whether any chemical weapons have been used does not inform us that the Assad regime has a brutal streak; we already knew that. Nor does it tell us that many Syrians are suffering in this civil war; we already knew that, too, and the suffering does not depend on any use of unconventional weapons. Most important for the policy question facing the United States, facts about chemical weapons use would tell us essentially nothing about the net effect of various forms of external intervention in the civil war, the likely course of the war with or without intervention, and possible political futures of Syria.

There is another parallel between today's debate about Syria and the counterpart discourse before the Iraq War. In each case the issue of unconventional weapons has been used as a convenient selling point by those favoring involvement in a war for other reasons. With Iraq, the WMD question was only, as later acknowledged by Paul Wolfowitz, a convenient topic that could be agreed upon by those who might disagree about other matters. With Syria, most of the current agitation is coming not from longstanding chemical-weapons-control enthusiasts but instead from those who had already been agitating for intervention on other grounds.

The agitators on Syria have been aided by President Obama's unwise earlier declaration about how use of chemical weapons by the Syrian regime would be a “game-changer.” Perhaps the president said this to help fend off the pro-intervention pressure he already was feeling at the time. If so, the remark was a short-sighted tactic. It opened the way for pro-interventionists to argue that U.S. credibility will be harmed if it does not now intervene in Syria.

That argument is also a familiar one associated with mistakes of the past. It also is invalid, as a matter of how people and governments actually assess the credibility of other governments. The argument was at the center—not just as a public selling point, but as a matter of genuine belief by policy-makers—of the decision to intervene in Vietnam in the mid-1960s. That war also was a blunder.

One might think, based on the current chemically-fueled commentary about Syria, that the ranks of the policy elite in Washington are filled with arms control aficionados whose fondest cause is to eliminate the scourge of unconventional weapons from the Middle East. Anyone who thinks that can be jolted back to reality by Egypt, which this week announced that it was pulling out of an ongoing review conference on the Nuclear Nonproliferation Treaty to protest the continued inaction on a resolution dating back to 1995 that calls for establishment of a nuclear weapons-free zone in the Middle East. That proposal was later expanded to envision a WMD-free zone in the Middle East, to include chemical and other unconventional weapons as well as nuclear ones. A conference, arranged under the leadership of a senior Finnish diplomat, was set to convene last December to discuss the proposal. But Israel refused to attend, and so the United States said it wouldn't go either, and the conference was called off. One barely heard a peep about that in the United States.

The country that balked, Israel, is of course the only Middle Eastern owner of nuclear weapons. That's nuclear weapons, which really are weapons of mass destruction, unlike chemical weapons, which aren't. In fact, the Israeli arsenal is so potent it is the only one that poses an existential threat to any other country in the region (and specifically to Iran).

U.S. policy, and American discussion of policy, about unconventional weapons in the Middle East have long been ridden with inconsistency. Nuclear weapons are perceived where they don't exist, and ignored where they do. The hyperventilation about possible use of chemical weapons in Syria is in the same tradition of inconsistency.