Oskar Lange or how IS-LM came to be interpreted as a Walrasian model

A few years after the publication of The General Theory, a number of economists began to present Keynes's model, identified with IS-LM, as a particular case of the Walrasian model. This view of IS-LM has often been rationalized by a basic syllogism: IS-LM was invented by John Hicks, Hicks was a Walrasian, hence IS-LM was Walrasian. But as some historians of macroeconomics have shown, this syllogism is false. Considering this confusion as an established fact, this article studies how and why IS-LM came to be considered as Walrasian. It shows that the standard view took its roots in "The Rate of Interest and the Optimum Propensity to Consume", a paper published by Oskar Lange in 1938, and resulted from a need to clarify the foundations of Keynes's theory.