Economics and Math

From a letter of Marshall to Bowley (taken from 'Economics for Mathematicians' by J.W.S. Cassels, Cambridge University Press):

"But I know I had a growing feeling in the later years of my work on 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 an engine of enquiry.

(2) Keep to them till you know you are done.

(3) Translate into English.

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

(5) Burn the mathematics.

(6) If you cannot succeed in 4, burn 3.

This last I did often."