"It's the principle now"

Somewhere around the fourth defence, the argument stops being about the roundabout. You can feel it change. It's now about whether you're the kind of person who gets bullied out of a view, or whether they always have to be right, or whether you're allowed an opinion in this house. The roundabout is long gone. What's left is the principle, and you can't climb down from a principle.

Look at how it got there. Ross, Lepper and Hubbard ran two experiments in 1975 in which people were given false feedback about how well they'd done at a task, and then told, thoroughly, that the feedback had been made up and had nothing to do with their performance. Their beliefs about their own ability persisted anyway. The evidence the belief was built on had been removed, and the belief stayed standing, in the person and in people watching. The researchers called it perseverance, and it's one of the most reliable things in the field. Beliefs outlive their reasons.

That's what's happened to the line. It was built on the roadworks not existing. The roadworks turned out to exist. The line should have fallen over at that point and instead it's still there, and because it's still there and has no reasons under it any more, it needs something else to hold it up. The principle is what it found. "It's not about the roundabout" is true, but not in the way it sounds. It's not about the roundabout because the roundabout stopped supporting the line ten minutes ago, and the line went looking for a new foundation.

The second argument, the one about the principle, is a different argument from the first one, and it's worth noticing that you're now having it. It's the argument about whether you were wrong in the first argument. It has no roadworks in it, nothing that could be checked, and no natural end. Two people can have it for years. And it started at exactly the moment the first argument was lost, which is the moment you could have said so.

Here's the useful thing about the second argument. It can't survive the five words. "I was wrong about the roundabout" ends the first argument, and the second one, having nothing to be about, ends with it. The principle, whatever it was, is still there for you to hold, on some other day about something that's actually about it.