680. Joan Robinson to Harrod , 16 June  [a]
[Replies to a letter not found, follows on from 677  ]
3, Trumpington Street, Cambridge
16 June 
My dear Roy
At least we seem to understand each other and can part agreeably each preferring his own method. I agree I read too much into your story of the 10 spindles. Indeed the whole of my point is that my method of statement gives two points on the new m.p. of capital curve, while yours only gives one, & my attempt to derive a second point from the data you gave was not legitimate.
[Fig. 1] I give points a) and b). You only give b).
You do not meet my second objection by your method, that it cannot deal with the Classical case. I get the annoying result that with constant/full [b] employment a capital-saving (Hicks) invention raises the rate of interest & a labour-saving (Hicks) one lowers it. I did not put this in my book for fear it seemed too shocking. This is a <bit of pain> you are debarred from by your method.
It seems to me if one can state the effect of an invention a) with constant rate of interest b) with constant employment one is in a better position to deal with actual cases in which intermediate movements take place. Anyway I can't see that it can do any harm to go into more detail.
It was only when our results seemed to be different that there was anything to argue about, & I plead guilty to misunderstanding what your "neutral" invention meant (as I explained, I think 3, letters ago  ), which caused most of the delay.
2. Letter 675 , [jump to page] .
- a. ALS, three pages on two leaves, in HP IV-1089-1107. Reproduced by kind permission of the Provost and Scholars, King's College, Cambridge.
b. The word "constant" was added as an afterthought above the word "full", the two words being united by a curly bracket:
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