GENTRIFICATION: Megan McArdle responds to a critic. “The rest of her post puts me in mind of the phenomenon that William Easterly has described in development circles: the recycling of ideas that have failed before, always unveiled with much fanfare, but no real explanation as to why this time is different. Frankly, it makes me understand why Easterly sometimes gets a little testy. . . . Perhaps it is unfair of me, but it seems to me that both Ms. Baca and her colleagues are mixing up their normative and their positive arguments. Because I say that we don’t know any way to preserve economically mixed neighborhoods, they essentially accuse me of ideological bad faith.” The recycling of ideas that have failed before, with no real explanation of why this time is different, describes much of the progressive project. And those who point this out are inevitably accused of bad faith, or worse. Sadly, the beat-down that McArdle applies is unlikely to have the necessary educational impact.