Karl Popper’s philosophy of science has been influential among economists, as among other scientists. Popper defends what he calls a falsificationist methodology (1968, 1969). Scientists should formulate theories that are “logically falsifiable” — that is, inconsistent with some possible observation reports. “All crows are black” is logically falsifiable; it is inconsistent with (and would be falsified by) an observation report of a red crow. (Probabilistic claims are obviously not in this sens