One widespread and pernicious illusion died a fiery death on September 11: The notion that America -- the "world's only superpower" -- was invulnerable and its people secure within their own borders against foreign attack was vaporized along with the World Trade Center towers, portions of the Pentagon and the hijacked jet aimed at the Capitol. It appears that two other dangerous illusions linger on, however. One involves the belief clung to by die-hard opponents of President Bush's efforts to develop and deploy effective missile defenses that we can safely perpetuate our complete vulnerability to another, far more deadly attack from ballistic missiles. The second is, if anything, even more preposterous: The belief that there are some "good" terrorists with whom we can prudently make common cause, at least temporarily, in waging war against the "bad" terrorists responsible for the events of 9/11. In coming days, Democratic members of Congress led by Rep. John Spratt of South Carolina and Senator Carl Levin of Michigan are expected to sunder the new-found bipartisan unity that has broken out in Washington since last week's attacks. They seek to make dramatic reductions in the levels of funding for the President's missile defense program and, in Sen. Levin's case, to impose in addition new legislative restrictions that would grievously hinder the use of any funds that may ultimately be approved for anti-missile systems. The proponents of such legislation evidently have a fairly low regard for the intelligence of their colleagues and the public. They apparently hope to sell the argument that, since ballistic missile defenses would not have stopped the passenger aircraft used by the terrorists this time, we should not be defended against what may be their weapon of choice the next time. Of course, this illusion flies in the face of common sense, to say nothing of the constitutional duty to provide for the common defense. Those who perpetrated these heinous crimes went to great lengths and considerable expense to inflict grave, but still relatively limited, damage on the nation they hate. They succeeded because the United States was unready to use defenses it does currently have to shoot down domestic commercial planes. Does anyone think for a moment, that if those waging holy war on this country, people fully prepared to die in the process of doing so, had access to weapons capable of inflicting infinitely greater death and destruction on us -- and against which we had no defense -- they would refrain from using them? Even more of an illusion, no a delusion, is the failure to appreciate a related point: The sponsors of terrorism, with whom President Bush has properly declared a state of war to exist, are working feverishly to acquire long-range ballistic missiles precisely so they can deter the sort of attack against their countries he has promised to launch. Would the United States really contemplate retaliation against Afghanistan if it could realistically threaten within 30 minutes to lay waste to the rest of New York City via missile-delivered weapons of mass destruction -- and our President could do nothing to prevent such a disaster? No less invidious than the illusory belief that the United States should be defended against some terrifying threats but not all of them is the sentiment now in evidence in Colin Powell's State Department. Officials in Foggy Bottom seem to feel that some sponsors of international terrorism can be recruited to wage Mr. Bush's war against other terrorist organizations and their hosts. Specifically, Yasser Arafat's Palestinian Authority, Bashar Assad's Syria and Ayatolloah Khameini's Iran are evidently being touted by some in the Administration as candidates for the new multinational coalition. This is one of the most impractical, not to say bizarre, ideas to come along in some time. For one thing, if President Bush's oft-repeated commitment to rid the world of terrorists and those who harbor them is to have any meaning -- to say nothing of any chance of producing the desired result -- he cannot be put in the position of turning a blind eye to some of the world's most notorious sponsors of terrorism. For another, American officials cannot really believe that the United States would be able to mount effective strikes on Osama bin Laden's organization, Al Qaeda, and some of his friends while sharing intelligence and operational details with coalition members who are also his friends, or who have, at least, made common cause with his terrorist campaigns against America, her interests and allies. The folly of this strategy, if it could be called such, would be greatly compounded by its corollary: In order to induce America's Arab enemies to participate in the new coalition, Israel will have to be excluded. Such a step would simultaneously deny the United States what may be its single best, and certainly most reliable, source of urgently needed intelligence and anti-terrorist skills. It would also be widely seen as implicit affirmation of the virulent attacks on Israel that the Bush Administration recently and wisely declined to dignify at the UN conference on racism in Durban, South Africa. After all, if Israel is deliberately excluded from the posse, there must be something to the charges that it is itself guilty of crimes against humanity. Those murdered in cold blood on September 11 will not have died in vain if we as a nation are spared the potentially far greater costs associated with these lingering illusions. It behooves President Bush and the Congress to work together to ensure that effective missile defenses are built and deployed at the earliest possible time and that any new alliance is made with fellow democracies who are victims of terrorism, not with terrorists who have violently assaulted them and us.