Alfred Marshall
on Math in Economics
Balliol 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...
I find mathematicians almost invariably follow what I regard as Jevons'
one great analytical mistake, his eulogy of the Geometric mean in general: and
do not see that, according to his use, erroneous weighting may do far more
mischief with the Geometric Mean than with the Arithmetic Mean. I always have to
spend some time in convincing them of the danger.
Your emptyhandedly,
Alfred Marshall
(The letter above was copied by
Eric
Rasmusen from pages 427-428 of
Memorials of Alfred Marshall, edited by A. C. Pigou. One edition is: New
York, A. M. Kelley, 1966, with Library of Congress catalogue number HB103 .M3
1966.)
