Sometimes the worst ideas are the ones that are so widely accepted as sensible -- or inevitable -- that almost nobody actually examines them. So it is among our country's political elites with the notion of invading Iraq and displacing Saddam Hussein as President of Iraq. The idea is so entrenched that when, last week, Hussein gave the Americans exactly what they'd demanded -- unconditional access for U.N. weapons inspectors -- not only did George Bush, predictably, dismiss the offer out of hand as a "ploy" and a "lie," but so did Tom Daschle, Richard Gephardt, and the rest of the Congressional Democratic leadership.

None of them, so far, have been willing to even consider the possibility of taking yes for an answer, because they're all wedded to a paradigm that makes invading Iraq sound awfully sensible. It goes like this: The United States can do anything it wants militarily. Saddam is bad. Saddam's oil is good. So why not get rid of him and take the oil? An invasion has other, lesser advantages as well -- particularly the intimidating example it provides for other governments that might one day consider serving their own, rather than American, interests -- but that's what it boils down to.

The problem is that there's a long list of very real answers to the rhetorical question of "why not?" Happily, a few of them are beginning to be raised on the fringes of American policy-making. But not enough. The challenge for the public, at this point, is to change the upcoming dynamic from an auto-blank check for whatever to an actual debate. Bush will get his permission, but if a high-profile debate can actually take place, that may create enough public unease to forestall an invasion. It's a long shot, but in our pseudo-democracy it's the only one we have. And to do it will require opposition that transcends ideology and focuses not on how we got here, but why this invasion is a very, very bad idea. Here are only a few of the most obvious reasons:

1) It's illegal. Forget George W. Bush's disingenuous "preemptive attack" rationale, and forget whatever U.N. Security Council resolutions the United States may be able to bribe other members into approving. Without being attacked by another country, the U.S. has no right to invade that country under either international law or the Geneva convention, the only two relevant legal guideposts. Ditto for unilaterally replacing the government of a sovereign foreign country. (Oh, and by the way: with who? Or what?) Contrary to conservatives who like to invoke Neville Chamberlain, Iraq has not invaded any other country since 1990, is not threatening to do so (nor could it), and the United Nations (which is to say, the U.S. with a fig leaf) decided upon a response in 1990 for the Kuwait transgression. Nobody at this point is claiming a new invasion of Iraq would be due to either the Kuwait invasion or any Iraqi links to 9/11.

2) It won't be easy. Obviously, the U.S. has lopsided military superiority -- that's the only kind of "war" our leaders seem to like, so truly treacherous governments, in countries like, say, Pakistan, are our allies instead. But this won't be turkey shoots on barren, exposed roads in the desert. Baghdad will be urban warfare, and contrary to the smug assertions of Albright, Rumsfeld, et al., most Iraqi people, along with most of the rest of the world's people, blame the United States, not Saddam Hussein, for Iraqis' massive suffering and death over the last decade. They won't be cheering and waving flags as soldiers from Kansas march into town. What sort of acts of outrage might people in this country be moved to, if a twentieth of our people had died by the callous hand of an arrogant foreign government? Forget 3,000 people in Manhattan, that would be more than the entire populations of New York City, Los Angeles, and Chicago combined.

And how would we respond if that foreign government then decided, after this campaign and all previous efforts to assassinate him had failed, to invade America to remove George Bush? Would we welcome them? Even if we hadn't voted Bush into office in the first place? (Oops. Scratch that.)

Remember Black Hawk Down? Most people don't like foreign soldiers in their city. Which brings us to...

3) A lot of people will die. Not many U.S. soldiers, of course, the Pentagon has learned its PR lessons, and the technological advantage is too overwhelming. But contrary again to the PR spin, if given a choice between killing a lot of civilians and losing a few soldiers, Iraq's civilians are dead meat. And that means...

4) A lot of people outside Iraq will die, too. For most Muslims, the catastrophe that has already befallen their Iraqi sisters and brothers dwarfs anything the U.S. has done in Afghanistan. And, in extreme cases, inflames their will toward terrorism. Both would likely be far, far worse with a new invasion. The "moderate" Arab and Islamic dictatorships that gladly accept U.S. money, weapons, and secret police training in exchange for a cut of the spoils are also all likely to become targets for populations already very, very tired of American backing of Israel and of the regime's most brutal thugs and thieves.

Moreover, the third complaint of Al-Qaeda (and many other less fanatical Muslims) along with Iraq and Palestine -- presence of the U.S. military in the holy land of Saudi Arabia -- is also likely to be escalated during an American invasion of Iraq. What it all adds up to is the serious risk of rebellions and spreading war throughout the region -- and use of the crisis by Israel to justify further atrocities against its occupied Palestinian population. The whole region could get very ugly in a hurry. Not does the bloodshed stop there...

5) Invading Iraq creates anti-Western, especially anti-American, terrorism everywhere. The U.S. invasion of Afghanistan and displacement of Al-Qaeda and the Taliban was a recruiting boon for radical Islamic fundamentalists, leading countless scores of thousands to pledge themselves to the same sort of anti-American jihad 19 people managed last September. That's nothing compared to the onslaught of new recruits that an attack on Iraq would produce. Saddam is just as hated by these folks -- he's the wrong branch of Islam and persecutes his fundamentalists, which is one of the reasons why the notion of his cooperation with groups like Al-Qaeda is so far-fetched. But the vision of still more Muslim blood being spilled in the Middle East at the hands of the American invaders will, as nothing else, make every person living in this country a target. And that, in turn, will doubtless make the lives of immigrants and "Muslim-looking" people throughout the U.S. more difficult, too. But illegality and the triggering of widespread violence aren't the only difficulties...

6) Iraq's oil fields are an environmental catastrophe waiting to happen. So, for that matter, are the ones in Saudi Arabia -- Iraq because an advancing American or retreating Iraqi government, or both, could create an environmental catastrophe far worse than the mess created in 1991 in Kuwait, and Saudi Arabia because terrorists or rebels could do the same thing to its hundreds of miles of pipelines and refineries and ports. And that's the good possibility. The bad one is that Saddam Hussein really does have chemical or biological weapons, in which case, he'd be insane (which he's not) to use them in any case except one -- as a last ditch effort to maintain power. Or, they could be released accidentally through military attack.

Either way, bad, bad news that wouldn't happen without an invasion. But the damage wouldn't just be over there...

7) It will tank our economy. Any damage to Iraqi or Saudi oil supplies would not only drive up the cost of oil here, but prove a crippling blow to an economy that's already in far more precarious shape than the relentlessly cheery "recovery" forecasts of economists and politicians would have you believe. Ask a war proponent if they're really willing to pay four bucks a gallon to gas up their supersized SUV. And concessions to the EU to gain support for an invasion would almost certainly involve trade concessions -- meaning a loss of price supports for farmers and other industries seemingly having nothing to do with Saddam Hussein, exactly at a time when they can least afford it.

8) Finally, Muslims are not the only people likely to be caught up in a renewed anti-Americanism. Resentment of U.S. unilateralism, arrogance, exceptionalism, and hypocrisy is already high in much of the world, and regardless of whatever resolutions or staged crises are used as the immediate pretext for an invasion, much of the world won't buy it. The DC notion is to use Iraq as an example to keep other governments in line, but the example cuts both ways -- it also ratchets up resentment of American empire throughout the world. And as America's military wades into conflicts on five continents -- over 60 countries, at last count -- that sort of resentment can play out in unpredictable ways. As can the example of one country unilaterally invading another to "prevent" a perceived threat; just as India, Israel, and Russia all promptly used the Bush invention of a doctrine of "harboring terrorists" to their own benefit. A green light for invading weaker countries could lead to a bloody escalation of any of the dozens of wars already simmering or raging throughout the world.

The bottom line: a U.S. invasion of Iraq will kill a lot of people, create an environmental catastrophe, set horrific international precedents, inflame an already-volatile region, inflame anti-Americanism around the world, risk environmental catastrophe, and put civilians in our own country at far greater risk of terrorist attack -- exactly what the Bush Administration allegedly set out to prevent in the original, long-forgotten premise of the War On Terror. And, interestingly, it was exactly the scenario Osama bin Laden dreamed of a year ago.

These sorts of fanciful colonial mapmaking exercises -- ordered, invariably, by men who've never actually seen what a war looks like -- have a way of bringing down arrogant, overreaching empires. And invariably, people like George Bush and Saddam Hussein are the last to suffer the consequences.

Arguments against an invasion are compelling on any of the above grounds -- let alone the procedural grounds, or through an examination of the breathtaking flimsiness of the Bush crew's professed rationale. (Has anyone, anywhere actually seen any evidence Saddam Hussein's government poses a threat to the United States?) But they need to be popularized, and given the upcoming debate on Capitol Hill, they need to be made, by a lot of people, to Senators and Representatives across the country. Phone, fax, write, e-mail, visit. And when you're done, get some friends to do it, too.

The above laundry list isn't comprehensive, but even what's on it is the stuff of nightmares. And we're the only ones who can stop it.