President Bush is right that the world is better off now that Saddam Hussein has been captured and can, for certain, no longer threaten his enemies and kill and torture his own people. However, the president is not right that it does not matter if weapons of mass destruction are found in Iraq.

The administration has changed the rationale for attacking Iraq as events have unfolded. But, the fact remains that the president and members of his cabinet said that Saddam Hussein possessed weapons of mass destruction and, therefore, was a threat to his neighbors and the world. When the fighting stopped and unimpeded weapons searches turned up no chemical, biological or nuclear weapons, the administration said there was evidence of an Iraqi weapons program. Mr. Hussein didn’t have them ready to go, the new reasoning went, but he could still make them.

Now that Mr. Hussein is in U.S. custody, the president has taken to saying that ridding the world of the horrid dictator is all that matters. Forget the weapons, he says.

But, Americans and especially lawmakers should not forget about the weapons. Congress OK’d the attacks on Baghdad not because Mr. Hussein was a tyrant, something he’d been for decades. The authorization came because Congress was told that the dictator had weapons of mass destruction. If the war was fought – and thankfully won – on the wrong premise, Congress should find out why.

It is interesting to see the change in semantics over time. “If we know Hussein has dangerous weapons today – and we do – does it make any sense for the world to wait to confront him as he grows even stronger and develops even more dangerous weapons,” the president said in October 2002, while building the case for war.

A year later, the U.S. chief weapons inspector, David Kay reported that he had yet to find any weapons in Iraq. Reprising Mr. Kay’s report in The Washington Post, Secretary of State Colin Powell wrote that the team did find “dozens of WMD-related program activities and significant amounts of equipment that Iraq concealed from the United Nations during inspections that began in 2002.” In the course of a year, the definitive “dangerous weapons today” became the more amorphous “WMD-related program activities.”

Now, the president has stepped even further from his October 2002 assertion. “If he were to acquire weapons, he would be a danger,” Mr. Bush said during an interview recently with Diane Sawyer of ABC News. But, the president concluded, Mr. Hussein’s weapons possession no longer matters because he is a prisoner.

But it does matter. Hans Blix, the former chief United Nation’s weapons inspector was asked shortly after the toppling of Mr. Hussein’s regime whether the WMD still mattered. “We’d all like to know whether there are any,” he said. “This was a major argument, after all, for starting the war. And then I think that’s natural that both the world and the U.S. public want to find out whether this particular argument was well founded or not.”

The world and the U.S. public still deserve to know.