I think in the world of economics, those are very fuzzy lines. Economics and law are full of conjecture, the belief that if one thing is true, others will probably be as well (see supply-side economics, Marxism, and so on), and the amount those views are clung to despite existing data is startling. I don't agree with the conclusions she comes to, but it's not a huge jump from what economists the Krugman do all the time.