Responding to a Noah Smith post, Brad DeLong offers a defense of the utlity of macroeconomic knowledge that basically blames partisanship and political paralysis rather than lack of knowledge for the failure of policy to do a better job of responding to a global depression.
I think the defense, such as it is, is actually incredibly damning. For starters, of DeLong's two groups of people with useful insights to offer—history-oriented students of the macroeconomy and central bank modelers—neither actually qualifies as doing what an academic department would call macroeconomics. It's a field, in other words, where practice (at the central banks) and the academic study of past practice (among economic historians) is leading theory rather than one in which persuasive theoretical conclusions are driving successful policy. That reality is intimately linked to what DeLong sees as a black hats vs white hats story of partisan pollution. The work that macroeconomic theorists and modelers do is genuinely difficult—certainly I can't do it—but it's far too easy for people with the relevant skills to demonstrate just about anything.