For Brad DeLong, Knowledge about a Topic...

Is just not necessary for spouting off authoritatively about it:

"After all, Ptolemy had microfoundations: Mercury moved more rapidly than Saturn because the Angel of Mercury left his wings more rapidly than the Angel of Saturn and because Mercury was lighter than Saturn..."

As far as I can tell, this is 100% made up. Angels were not a part of Greek belief, and the idea that angels had something to do with the planetary orbits does not seem to arise until the Middle Ages. Now, if you want an example of someone who did think angels moved the planets, Kepler would work: but then things get awkward, as he was a hero of the Scientific Revolution, which is supposed to be all about jettisoning such beliefs.


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