The central sickness of human history is the notion that the ends justify the means, and it has disastrously gripped political movements from left to right and from the secular to the religious. It is axiomatic that immoral means will inevitably corrupt the noblest of ends, as has been displayed from the fatal hubris of the Roman Empire down through the genocidal policies of the last century’s nationalists, communists and colonialists and on through the suicide bombers of today.

Yet this profoundly immoral posture has been embraced by President Bush in justifying his preemptive war against Iraq, even when the much-touted Iraqi threat proved at best to be based on inexcusable ignorance and at worst to be impeachable fraud. The undemocratic means employed by Bush–misinforming the public, Congress and the United Nations–are now somehow to be justified by the ends of “building democracy” in Iraq. This is a daunting challenge that the American people never signed on for and which seems as elusive a goal today as a year ago.

Once again we seem unwilling to fully grasp the lesson of Vietnam, our other major exercise in preemptive war based on the theories of ivory-tower intellectuals with dreams of a Pax Americana. For those requiring a refresher course in that previous folly, which so fractured our own country while devastating three others, check out the new documentary The Fog of War, in which the Vietnam adventure’s prime architect, Robert S. McNamara, tearfully concedes it was all a grand mistake.

That decadelong conflict was brought to you originally by Democrats, one of whom, John F. Kennedy, remains much admired. McNamara attempts to make the case that JFK wanted to get out but was assassinated before that could happen, but I don’t buy that theory. Getting out is the hardest part, particularly once you have put abroad the lie that you invaded a country in order to save it. It is political suicide to then abandon such a crusading war when it turns sour.

Today, in Iraq, we again have been battered senseless by the argument that it is “irresponsible” to leave, even when it is clear we are no longer welcome. Those who dare suggest that our continued presence as an occupier is actually part of the problem–like presidential candidate Rep. Dennis J. Kucinich (D-Ohio)–are pilloried as unrealistic. But attempting to alter other people’s history–while also serving our own economic and political needs–leads almost inevitably to quagmire, blowback and a nonsensical path of trying to make future truth of past lies: We didn’t go to Iraq to save it, but now we have to save it to excuse the fact that we went.

This tangled web is no less onerous when spun by Republicans Bush and Dick Cheney than by Democrats Kennedy and Lyndon B. Johnson. And now, as then, in the early stages of the war we saw only the most tepid opposition from the political and media elites to the big-lie technique that so often accompanies war.

Most of the leading Democratic Party presidential candidates, for example, are compromised by having supported an invasion they should have passionately challenged before it was launched. It is not too late for them to admit they were fooled by Bush, as some of them have begun to do. Thankfully, the campaign of Sen. Joe Lieberman (D-Conn.) is on the ropes. He has consistently endorsed the White House’s cynical abuse of the facts; just last week, he said the Iraq invasion was “just” because “Saddam Hussein himself was a weapon of mass destruction,” a stupid and dangerous twisting of language.

Similarly unnerving is the ease with which ideologues like Deputy Defense Secretary Paul D. Wolfowitz manage to shape and shift their arguments whenever their grand theories are undermined by messy reality. “We have a more important job to do in Iraq…and that is to help the Iraqi people build a free and democratic country,” Wolfowitz said last weekend.

If this was the goal all along, then why didn’t Wolfowitz and Bush tell the American people before they sacrificed their sons and daughters to the crusade? What was all that about the imminent threat of Iraq’s weapons of mass destruction and Hussein’s ties to 9/11? All lies, it turns out. If Wolfowitz ever finds his conscience as McNamara apparently has, he too will be crying in some future documentary about the folly of presuming to bring enlightenment to a people we neither respected nor understood, while undermining our own fragile democracy.