Lachmann, Keynes, and Subjectivism

The Austrian economist Ludwig Lachmann claimed that Keynes was a lifelong subjectivist. To evaluate this, we start by distinguishing Keynes’ writings on probability theory from his writings on economics. In the General Theory (1936), Keynes’ treatment of expectations provides the basis for Lachmann’s view that Keynes was a subjectivist at heart. In his Treatise on Probability (1921), Keynes refers explicitly to the subjectivism–objectivism divide in probability theory and pins his colors to the objectivist mast. In this essay, we present the objectivist slant in Keynes’ earlier writings on probability theory. Thereafter, we evaluate the criteria Lachmann employed to cast Keynes as a subjectivist.