It was a spectacular performance, and by the time Colin Powell was finished, I was a complete convert. But what, exactly, have I been converted from and to? It's a question I've been turning over in my mind ever since last Wednesday's tour de force before members of the U.N. Security Council. I am, for one thing, converted to the idea that Iraqi President Saddam Hussein is in "material breach" of the U.N. mandate he was required to carry out. Before the Powell show, the analogy in my head was of sheriff's deputies executing a search warrant. It was an...