Before the 1970s, the discussion of how to make economics a science was left mostly to economists. But like war, which is too important to be left to the generals, economics was too important to be left to the Nobel-winning members of the University of Chicago faculty. Over time, the question of why economics has not (yet) qualified as a science has become an obsession among theorists, including philosophers of science like us.
It’s easy to understand why economics might be mistaken for science. It uses quantitative expression in mathematics and the succinct statement of its theories in axioms and derived “theorems,” so economics looks a lot like the models of science we are familiar with from physics. Its approach to economic outcomes — determined from the choices of a large number of “atomic” individuals — recalls the way atomic theory explains chemical reactions. Economics employs partial differential equations like those in a Black-Scholes account of derivatives markets, equations that look remarkably like ones familiar from physics. The trouble with economics is that it lacks the most important of science’s characteristics — a record of improvement in predictive range and accuracy.
This is what makes economics a subject of special interest among philosophers of science. None of our models of science really fit economics at all.
The irony is that for a long time economists announced a semiofficial allegiance to Karl Popper’s demand for falsifiability as the litmus test for science, and adopted Milton Friedman’s thesis that the only thing that mattered in science was predictive power. Mr. Friedman was reacting to a criticism made by Marxist economists and historical economists that mathematical economics was useless because it made so many idealized assumptions about economic processes: perfect rationality, infinite divisibility of commodities, constant returns to scale, complete information, no price setting.