One thing is for certain, though, about me, and the world has learned this: When I say something, I mean it. And the credibility of the United States is incredibly important for keeping world peace and freedom.

That's the summation President Bush delivered as he wrapped up his press conference Tuesday night. It's the message he emphasized throughout: Our commitment. Our pledge. Our word. My conviction. Given the stakes in Iraq and the war against terrorism, it would be petty to poke fun at Bush for calling credibility "incredibly important." His routine misuse of the word "incredible," while illiterate, is harmless. His misunderstanding of the word "credible," however, isn't harmless. It's catastrophic.

"A free Iraq will confirm to a watching world that America's word, once given, can be relied upon," he argued Tuesday night. When the situation is clear and requires pure courage, this steadfastness is Bush's most useful trait. But when the situation is unclear, Bush's notion of credibility turns out to be dangerously unhinged. The only words and deeds that have to match are his. No correspondence to reality is required. Bush can say today what he said yesterday, and do today what he promised yesterday, even if nothing he believes about the rest of the world is true.

Outside Bush's head, his statements keep crashing into reality.

As to the WMD, Bush said the chief U.S. weapons inspector in Iraq had confirmed that Iraq was "hiding things. A country that hides something is a country that is afraid of getting caught." See the logic? A country that hides something must be afraid of getting caught, and a country afraid of getting caught must be hiding something. Each statement validates the other, sparing Bush the need to find the WMD.

To many Americans, the gap between Bush's statements about the months before 9/11, on the one hand, and the emerging evidence about those months, on the other, raises doubts about the credibility of their government. To other nations, the gap between Bush's statements about Iraqi weapons, on the one hand, and the emerging evidence about those weapons, on the other, has become the central reason to distrust the United States in other matters of enormous consequence, such as North Korea's nuclear program.

To all of this, however, Bush is blind. He doesn't measure his version of the world against anybody else's. He measures his version against itself. He says the same thing today that he said yesterday. That's why, when he was asked Tuesday whether he felt any responsibility for failing to stop the 9/11 plot, he kept shrugging that "the country"--not the president--wasn't on the lookout. It's also why, when he was asked to name his biggest mistake since 9/11, he insisted, "Even knowing what I know today about the stockpiles of weapons [not found in Iraq], I still would've called upon the world to deal with Saddam Hussein." Bush believes now what he believed then. Incredible, but true.