The warm tone of the letter from White House insider Lewis "Scooter" Libby to Judith Miller of the New York Times conveyed an essential reality of reporter-source relationships, which we in the media sometimes tend to play down: These are often relationships between like-minded people who care about the same issues and who become -- dare I say it? -- friendly.

"Your reporting, and you, are missed," began Vice President Cheney's chief of staff in his Sept. 15 letter releasing Miller from any pledge of confidentiality and urging her to testify in the Valerie Plame leak investigation. "You will have stories to cover -- Iraqi elections and suicide bombers, biological threats and the Iranian nuclear program. Out West, where you vacation, the aspens will already be turning. They turn in clusters, because their roots connect them. Come back to work -- and life."

It's obvious that Libby cares about Miller and wants her to return to reporting on issues they both see as important. That sort of personal connection between reporter and source may strike some people as sinister, but it's the mother's milk of journalism. That's why people tell us things: Because we listen, and often sound sympathetic. Just ask Bob Woodward. But the true measure of a great reporter, as Woodward has shown time and again, is a willingness to bite the hands that feed you. And the measure of a great newspaper is editors who insist on that ultimate separation of reporter and source, but we'll come back to that.

I have no idea what further investigation will reveal about the discussions in the summer of 2003 between Miller and Libby. But I wouldn't be surprised if the evidence showed what's already obvious -- that she and Libby both cared deeply about whether Saddam Hussein had weapons of mass destruction, and were frustrated by the failure to find any. Miller had won a Pulitzer Prize for her reporting on biological weapons, and she had spent many weeks in Iraq with the weapons survey group in a fruitless search for those weapons.

Journalists come in two basic varieties, hot and cold. Miller has always been the former. I've known her for 30 years, and I have seen the intensity that leads her to throw herself into story after story. She's being flayed now on the left because her reporting on WMD was too credulous, especially of self-interested sources such as Iraqi exile leader Ahmed Chalabi. But Miller was also one of the few reporters in the world who got the Osama bin Laden story right before Sept. 11.

Passionate is good when you agree with it and bad when you don't. That's the conclusion I draw from recent praise for crusading, engaged, sometimes tearful coverage of Hurricane Katrina by journalists such as NBC's Brian Williams and CNN's Anderson Cooper. I've always admired the dry-bones approach more, but I understand why people want journalists to lean into the story.

The big lesson of the Miller affair, for me, is that editors are crucial in mediating the relationships between reporters and sources. Almost by definition, those relationships become incestuous -- with journalists and their sources chasing the same facts and often seeking to right the same wrongs. It's the job of editors to intervene in this process -- and demand to know, on behalf of readers, whether a story is really true. In Miller's case, she filed stories about Iraqi weapons of mass destruction based on what her sources had told her, but the crucial judgment lay in the hands of her editors.

This process of editorial intervention is even more important when it comes to making promises to sources about confidentiality. Reporters shouldn't be able to decide unilaterally to whom they will attach their newspaper's reputation. Editors should agree to absolute confidentiality only in the rarest cases. In my years as an editor, I often asked reporters to go back and tell an anonymous source that if we got sued based on what he had told us, we wanted the right to subpoena that source and his records, to defend ourselves. If the source refused, sometimes we would walk away; other times, based on the importance of the information to the public, we would extend the absolute protection he requested. Some version of that Miranda warning to sources seems essential to me.

When Miller emerged from prison, she urged passage of a federal shield law, and she's right about that. But while we're waiting for a media-friendly Congress, we journalists should look more closely at our own rules. Reporters and their sources shouldn't determine a newspaper's agenda, much less whether a reporter should go to jail in defiance of a grand jury subpoena. That's a job for editors and their publishers.