We might test judgment by asking, on the issue of Iraq, who best anticipated how events turned out. But many of those who correctly anticipated catastrophe did so not by exercising judgment but by indulging in ideology. They opposed the invasion because they believed the president was only after the oil or because they believed America is always and in every situation wrong.

The people who truly showed good judgment on Iraq predicted the consequences that actually ensued but also rightly evaluated the motives that led to the action. They did not necessarily possess more knowledge than the rest of us. They labored, as everyone did, with the same faulty intelligence and lack of knowledge of Iraq’s fissured sectarian history. What they didn’t do was take wishes for reality. They didn’t suppose, as President Bush did, that because they believed in the integrity of their own motives everyone else in the region would believe in it, too. They didn’t suppose that a free state could arise on the foundations of 35 years of police terror. They didn’t suppose that America had the power to shape political outcomes in a faraway country of which most Americans knew little. They didn’t believe that because America defended human rights and freedom in Bosnia and Kosovo it had to be doing so in Iraq. They avoided all these mistakes.

I made some of these mistakes and then a few of my own. The lesson I draw for the future is to be less influenced by the passions of people I admire — Iraqi exiles, for example — and to be less swayed by my emotions. I went to northern Iraq in 1992. I saw what Saddam Hussein did to the Kurds. From that moment forward, I believed he had to go. My convictions had all the authority of personal experience, but for that very reason, I let emotion carry me past the hard questions, like: Can Kurds, Sunnis and Shiites hold together in peace what Saddam Hussein held together by terror? I should have known that emotions in politics, as in life, tend to be self-justifying and in matters of ultimate political judgment, nothing, not even your own feelings, should be held immune from the burden of justification through cross-examination and argument.

Good judgment in politics, it turns out, depends on being a critical judge of yourself. It was not merely that the president did not take the care to understand Iraq. He also did not take the care to understand himself. The sense of reality that might have saved him from catastrophe would have taken the form of some warning bell sounding inside, alerting him that he did not know what he was doing. But then, it is doubtful that warning bells had ever sounded in him before. He had led a charmed life, and in charmed lives warning bells do not sound.

People with good judgment listen to warning bells within. Prudent leaders force themselves to listen equally to advocates and opponents of the course of action they are thinking of pursuing. They do not suppose that their own good intentions will guarantee good results. They do not suppose they know all they need to know. If power corrupts, it corrupts this sixth sense of personal limitation on which prudence relies.

A prudent leader will save democracies from the worst, but prudent leaders will not inspire a democracy to give its best. Democratic peoples should always be looking for something more than prudence in a leader: daring, vision and — what goes with both — a willingness to risk failure. Daring leaders can be trusted as long as they give some inkling of knowing what it is to fail. They must be men of sorrow acquainted with grief, as the prophet Isaiah says, men and women who have not led charmed lives, who understand us as we really are, who have never given up hope and who know they are in politics to make their country better. These are the leaders whose judgment, even if sometimes wrong, will still prove worthy of trust.