## Mathematical economics — an unmixed evil

29 Mar, 2018 at 18:15 | Posted in Economics | 2 CommentsBalliol Croft, Cambridge

27. ii. 06

My dear Bowley,I have not been able to lay my hands on any notes as to Mathematico-economics that would be of any use to you: and I have very indistinct memories of what I used to think on the subject. I never read mathematics now: in fact I have forgotten even how to integrate a good many things.

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 short-hand 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.

I believe in Newton’s Principia Methods, because they carry so much of the ordinary mind with them. 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 …

Your emptyhandedly,

Alfred Marshall

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The faith in math that many mainstream economists profess seems to me to often be married to utter contempt for natural language, to such an extent that they do not take seriously anything said or written in natural language — even their own statements are not meant as serious engagements. I suppose if you do not want to be questioned regarding reality, making yourself unable to answer is a solution.

Comment by Bruce Wilder— 29 Mar, 2018 #

Lay to that J.M Keynes a ardent student of Marshall, in the General Theory:

“It is a great fault of symbolic pseudo-mathematical methods of formalizing a system of economic analysis…that they expressly assume strict independence between the factors involved and lose all their cogency and authority if this hypothesis is disallowed; whereas, in ordinary discourse, where we are not blindly manipulating but know all the time what we are doing and what the words mean, we can keep “at the back of our heads” the necessary reserves and qualifications and the adjustments which we shall have to make later on, in a way in which we cannot keep partial differentials “at the back” of several pages of algebra which assume that they all vanish. Too large a proportion of recent “mathematical” economics are mere concoctions, as imprecise as the initial assumptions they rest on, which allow the author to lose sight of the complexities and interdependencies of the real world in a maze of pretentious and unhelpful symbols.” (pp. 297-298)

Comment by Jan Milch— 30 Mar, 2018 #