Keynes and the Financial Markets. Halfway from "homo economicus" to "homo humanus"

John Maynard Keynes was an economist who constantly oscillated between the world of theories and reality, he tested and rejected theoretical assumptions based on his observations, which he in turn used as starting points for the development of new theories. At the same time, as a practitioner, he did not engage in any other type of activity with such intensity and continuity as financial transactions of any kind. These experiences made it clear to Keynes that economic behaviour is essentially shaped by uncertainty, emotions and social interaction. In his analysis of trading behaviour and price dynamics on financial markets (which anticipates the most important developments since the 1970s), he sketches an image of man that is radically opposed to that of "homo oeconomicus". However, he did not elaborate theoretically this realistic micro-foundation of his macroeconomics. If he had, he would have had to explicitly reject the entire neoclassical theory. But this would have contradicted the main goal of his "General Theory", which was to reach his "fellow economists" with his theory of employment, interest rates and money where they were.