Lars P. Syll — Paul Samuelson and the ergodic hypothesis

Paul Samuelson deserves a lot of the blame for what happened owing to his influence on economic methodology. But it did not begin with Samuelson. Keynes criticized Tinbergen's econometrics, for example, and Alfred Marshall, whose Principles was as influential at the time as was Samuelson subsequently, also warned about overextending the use of mathematics.

The rigor of scientific method in causal explanation stems from balancing intuition in discovery, mathematical formalism in theory construction, and empirical data as the basis of evidence in testing hypotheses.

Formalists lost the plot, which is providing naturalistic causal explanation of natural phenomena (objects and events). They conflated science with modeling and overly minimized the significance of interpreting of theory in terms of data. They also ignored the influence of institutional arrangements, which MMT has attempted to correct regarding the relationship of economics, finance, accounting, law, and policy.

This was disastrous for economics since the subject matter of social science, and also life science to a great extent, is fundamentally different from the subject matter of natural science. The subject matter of natural science is ergodic and social science is non-ergodic for reasons Lars Syll cites in the references he provides in the post. 

Time makes a difference in social science. As Karl Marx emphasized, economics is historical.

See Ole Peters. The ergodicity problem in economics. Nature Physics volume 15, pages1216–1221(2019)

Abstract
The ergodic hypothesis is a key analytical device of equilibrium statistical mechanics. It underlies the assumption that the time average and the expectation value of an observable are the same. Where it is valid, dynamical descriptions can often be replaced with much simpler probabilistic ones — time is essentially eliminated from the models. The conditions for validity are restrictive, even more so for non-equilibrium systems. Economics typically deals with systems far from equilibrium — specifically with models of growth. It may therefore come as a surprise to learn that the prevailing formulations of economic theory — expected utility theory and its descendants — make an indiscriminate assumption of ergodicity. This is largely because foundational concepts to do with risk and randomness originated in seventeenth-century economics, predating by some 200 years the concept of ergodicity, which arose in nineteenth-century physics. In this Perspective, I argue that by carefully addressing the question of ergodicity, many puzzles besetting the current economic formalism are resolved in a natural and empirically testable way.

Lars P. Syll’s Blog

Paul Samuelson and the ergodic hypothesis
Lars P. Syll | Professor, Malmo University

See also

The Radford Free Press
“A Primer For the Perplexed”
Peter Radford