The kernel of Krugman’s post is a Planet Money podcast about a perennial favorite of theirs.
A good read for those thinking about theories, the equilibrium-rationality paradigm, and agent-based modeling. A good listen for those thinking about history, the macroeconomy, and politics. Planet Money blogs a bit more directly on the matter, too.
Hat tip to Dave Dixon for Krugman’s comment. The connection between those two is David Glasner’s post, another useful read for thinking about theories and history.