Should-Read: Very smart pickup about teaching—and doing—economics from Paul Romer and Alfred Marshall by the highly estimable Tim Taylor: Tim Taylor: Some Thoughts About Economic Exposition in Math and Words: “[Paul Romer’s] notion that math is ‘both more precise and more opaque’ than words is an insight worth keeping…

…It reminded me of an earlier set of rules from the great economist Alfred Marshall, who… wrote in 1906 letter to Alfred Bowley (reprinted in A.C. Pigou (ed.), Memorials of Alfred Marshall, 1925 edition, quotation on p. 427): 

But I know I had a growing feeling in the later years of my work at the subject that a good mathematical theorem dealing with economic hypotheses was very unlikely to be good economics; and I went more and more on the rules:

  1. Use mathematics as a shorthand language; rather than as an engine of inquiry.

  2. Keep to them till you have done.

  3. Translate into English.

  4. Then illustrate by examples that are important in real life.

  5. Burn the mathematics.

  6. If you can’t succeed in 4, burn 3.

This last I did often…. Mathematics used in a Fellowship thesis by a man who is not a mathematician by nature—and I have come across a good deal of that—seems to me an unmixed evil. And I think you should do all you can to prevent people from using Mathematics in cases in which the English language is as short as the Mathematical…


Brad DeLong


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