Research Topics

An Assessment from Popper’s Philosophy

The rational expectations hypothesis (REH) is the standard approach to expectations formation in macroeconomics. We discuss its compatibility with two strands of Karl Popper´s philosophy: his theory of knowledge and learning, and his “rationality principle” (RP). First, we show that the REH is utterly incompatible with the former. Second, we argue that the REH can nevertheless be interpreted as a heuristic device that facilitates economic modeling and, consequently, it may be justified along the same lines as Popper´s RP. We then argue that, our position as to the resolution of this paradox notwithstanding, Popper´s philosophy provides a metatheoretical framework with which we can evaluate the REH. Within this framework, the REH can be viewed as a heuristic device or strategy that fulfils the same function as, for instance, the optimizing assumption. However, we believe that the REH imparts a serious methodological bias, since, by implying that macroeconomic instability is caused exclusively by “exogenous” shocks that randomly hit the economy, it precludes the analysis of any sources of inherent instability caused by the making of (nonrandom) errors by individuals, and hence it favors the creation of an institutional configuration that may be ill suited to address this type of instability.

The Queen of England famously asked her economic advisers why none of them had seen “it” (the global financial crisis) coming. Obviously, the answer is complex, but it must include reference to the evolution of macroeconomic theory over the postwar period—from the “Age of Keynes,” through the Friedmanian era and the return of Neoclassical economics in a particularly extreme form, and, finally, on to the New Monetary Consensus, with a new version of fine-tuning. The story cannot leave out the parallel developments in finance theory—with its efficient markets hypothesis—and in approaches to regulation and supervision of financial institutions.

This paper critically examines these developments and returns to the earlier Keynesian tradition to see what was left out of postwar macro. For example, the synthesis version of Keynes never incorporated true uncertainty or “unknowledge,” and thus deviated substantially from Keynes’s treatment of expectations in chapters 12 and 17 of the General Theory. It essentially reduced Keynes to sticky wages and prices, with nonneutral money only in the case of fooling. The stagflation of the 1970s ended the great debate between “Keynesians” and “Monetarists” in favor of Milton Friedman’s rules, and set the stage for the rise of a succession of increasingly silly theories rooted in pre-Keynesian thought. As Lord Robert Skidelsky (Keynes’s biographer) argues, “Rarely in history can such powerful minds have devoted themselves to such strange ideas.” By returning to Keynes, this paper attempts to provide a new direction forward.