Richard Kahn was Maynard Keynes’s favourite pupil.

At the end of his life Kahn said he was happy to be regarded as a disciple of Keynes. However, it may be argued that Kahn was much more than either of these (which is not meant to downgrade either of them).

Kahn was born in London in 1905 into a Jewish family of German origin. His family combined strict religious observance with a passion for education. Kahn went to St Paul’s School for Boys. (Joan Robinson, his greatest intellectual friend, went to St Paul’s School for Girls.) He came up to Cambridge in 1926, to King’s College. For the first three years he read mathematics, obtaining a First, and then physics, in which he obtained a Second and a notorious reputation for clumsiness and breakages at laboratory practicals. He stayed on for a fourth year, reading for Part II of the Economics Tripos. Kahn was supervised by Gerald Shove and Keynes. He obtained a First, a remarkable performance. This was followed by an even more remarkable achievement. He wrote, in just over one and a half years, a Fellowship dissertation for King’s, “The economics of the short period”, which was highly praised by Pigou and Keynes.

In his dissertation Kahn (1929) made the short period a topic worthy of study in its own right, especially in periods of recession or depression when the ceteris paribus assumption of a given stock of capital goods held for long stretches of calendar time. In the dissertation, sadly only published in English in 1989, just after Kahn died, are to be found the principal propositions of the imperfect/monopolistic competition “revolutions”, including the kinked demand curves of competing oligopolists. Moreover, the theoretical propositions are supported by empirical data on the UK staple industries, especially textiles, which Keynes made available to Kahn. When Joan Robinson was writing her Economics of Imperfect Competition (1933), Kahn was her most invaluable guide and critic, selflessly putting many of his own findings and methods into her book.

In her preface she refers to his “constant assistance” and writes that the “whole technical apparatus was built up with his aid [, that] major problems... were solved... by him” (Robinson 1933: v).

Keynes had Kahn read the proofs and prepare the index of A Treatise of Money (Keynes 1930), and then subsequently to provide the formal arguments to back up the conjectures of Hubert Henderson and Keynes in their 1929 pamphlet “Can Lloyd George do it?”. This led Kahn, together with James Meade, who was in Cambridge at this time and who was a member of the “Circus” which met to discuss Keynes’s 1930 volumes, to formulate the multiplier. The latter is a precise expression, under explicit conditions, of how much secondary employment would be created by a given rise in primary employment associated with, say, public works expenditure (Kahn 1931). The article became an integral part of the structure of The General Theory (Keynes 1936), especially in Keynes’s formulation of the consumption function.

Kahn was always sceptical of the quantity theory of money as constituting a causal mechanism in the determination of the general price level. He thought that the “fundamental equations” of A Treatise of Money could explain both the general price level and its sectorial counterparts without any need to refer to the quantity of money - even though Keynes himself argued that he was working within the quantity theory framework. Kahn’s emphasis on the short period and his scepticism about the quantity theory were the greatest direct influences on Keynes as he moved from the system of A Treatise on Money to the revolutionary system of The General Theory. Kahn was also the most important influence by far of the small group of people Keynes consulted while writing The General Theory. For example, Keynes wrote to Joan Robinson on 29 March 1934 that he was “going through a stiff week’s supervision from RFK... there never was anyone in the history of the world to whom it was so helpful to submit one’s stuff” (C.W., vol XIII, 1973, 422).

Kahn published important papers in a number of areas in the 1930s - on the elasticity of substitution, on ideal output, and on duopoly, for example. When war came he took to the Civil Service like a duck to water. He had an excellent war, being much in demand for his wise help in policy making combined with his meticulous attention to detail. During the war years he wrote a full-length manuscript on buffer stock schemes to stabilize the prices of primary products which alas was never published.

After the war he was mostly in Cambridge in a splendid set of rooms in Webb’s Court, King’s. He was appointed to a Chair in 1951 when he gave up the senior bursarship of King’s, a post he was appointed to following Keynes’s death in 1946. He was made a life peer in 1965, Baron Kahn of Hampstead. Kahn worked closely with Joan Robinson and later Luigi Pasinetti in developing post-Keynesian theories of distribution and growth, what Joan Robinson called generalizing The General Theory to the long period. His 1959 paper in Oxford Economic Papers is the clearest account of the nature, achievements and limitations of Golden Age - steady state - growth theory. He was also closely associated with the parallel critique of the conceptual foundations of the mainstream theory of value and distribution. Kahn wrote an important paper on the concept of the valuation ratio (a close cousin of Tobin’s q) in the 1960s (though it was not published until 1972; Kahn 1972a).

In the 1950s Kahn extended Keynes’s liquidity preference theory of the rate of interest to the stock market. He was one of the most important contributors to the Radcliffe Committee on the monetary system in 1958, in effect feeding into its pages a qualitative version of endogenous money theory. He also gave lectures on the need to establish a permanent incomes policy if full employment was to be sustained. In the 1970s and 1980s, in his British Academy Keynes Lecture (1975), an article in the Journal of Economic Literature (1978), and his Mattioli lectures (1984), he set out his accounts of the making of The General Theory, accounts which are insightful and definitive.

A selection of his most important articles were brought together in 1972 by Cambridge University Press (Kahn 1972b). Had his dissertation been published in the 1930s (he later wished that it had been), it and his 1931 multiplier article would surely have meant the award of a (akin to) Nobel Prize in economics.

Especially in later years when he was very deaf and suffering ill health, Kahn seemed outwardly a forbidding and remote figure. However, to his friends he was as loved as ever for his thoughtfulness, consideration and loyalty, albeit all were still wary of his notoriously fierce temper when he was displeased. He had been a byword for orthodoxy as a young man. He returned to the beliefs of his youth in his old age and was buried with his prayer shawl and phylacteries in the Jewish section of the Cambridge cemetery. Kahn never married but he never lacked agreeable female company either.

G.C. Harcourt

Richard Kahn was Maynard Keynes’s favourite pupil.

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