Back during the early days of the Iraq debacle, I learned that the military has a term for how highly dubious ideas become not just accepted, but viewed as certainties. “Incestuous amplification” happen when a closed group of people repeat the same things to each other – and when accepting the group’s preconceptions itself becomes a necessary ticket to being in the in-group. A fundamentally flawed notion – say, that the Germans can’t possibly attack though the Ardennes – becomes part of what everyone knows, where “everyone” means by definition only people who accept the flawed notion.

We saw that in the run-up to Iraq, where perfectly obvious propositions – the case for invading is very weak, the occupation may well be a nightmare – weren’t so much rejected as ruled out of discussion altogether; if you even considered those possibilities, you weren’t a serious person, no matter what your credentials.

Which brings me to the fiscal debate, characterized by the particular form of incestuous amplification Greg Sargent calls the Beltway Deficit Feedback Loop. I’ve already blogged about my Morning Joe appearance and Scarborough’s reaction, which was to insist that almost no mainstream economists share my view that deficit fear is vastly overblown. As Joe Weisenthal points out, the reality is that among those who have expressed views very similar to mine are the chief economist of Goldman Sachs; the former Treasury secretary and head of the National Economic Council; the former deputy chairman of the Federal Reserve; and the economics editor of the Financial Times. The point isn’t that these people are necessarily right (although they are), it is that Scarborough’s attempt at argument through authority is easily refuted by even a casual stroll through recent economic punditry.

But these people aren’t part of the in-group, and if they do make it into the in-group’s conversation at all, it’s only by blurring their message sufficiently that the in-group doesn’t understand it.

And at this point, of course, all the Very Serious People have committed their reputations so thoroughly to the official doctrine that they almost literally can’t hear any contrary evidence.