# Correcting Paul Samuelson’s Small Error in His November, 1963 Eulogy for Robertson: Dennis Robertson Erred Seriously in His Evaluation of Keynes’s Differential Calculus–Based Multiplier Concept in the General Theory

13 Pages Posted: 4 Nov 2018

Date Written: October 13, 2018

### Abstract

Dennis Robertson had no understanding of how J M Keynes’s Multiplier concept was based on the use of differential calculus techniques that required one to take the mathematical limit of an infinite, decreasing, geometric series. Robertson failed to see that the derivative concept requires that one is dealing with an instantaneous rate of change. Robertson thus confused the fact that the actual multiplier process of change in the real world is not instantaneous, but requires time for the process to actually function, so that in the real world it is not instantaneous, with the mathematical theory of the multiplier. Samuelson overlooked Robertson’s very confused state of mind, resulting from his mathematical illiteracy, when he concluded that Robertson’s criticisms of Keynes’s instantaneous, theoretical multiplier concept discussions on pages 122-123 of the General Theory were sound.

D. Robertson ‘s confused attempts at critiquing Keynes’s concepts of the logical theory of the multiplier and the multiplier in 1936 in his QJE article were due to his own extreme mathematical limitations, confusions and ineptness. Samuelson had recognized that this problem of mathematical illiteracy existed in the economics profession by 1936. Economists were shockingly unprepared in the use of even basic intermediate algebra.

**Keywords:** Samuelson, Robertson, Mathematical Illiteracy, Keynes, Differential Calculus, Multiplier, Marginal Propensity to Consume

**JEL Classification:** B10, B12, B14, B16, B20, B22

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