Keynes didn’t make an all-out assault on Economic Man, but he often resorted to plausible psychological theorizing rather than careful analysis of wh… - Paul Krugman

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Keynes didn’t make an all-out assault on Economic Man, but he often resorted to plausible psychological theorizing rather than careful analysis of what a rational decision-maker would do. Business decisions were driven by “animal spirits,” consumer decisions by a psychological tendency to spend some but not all of any increase in income, wage settlements by a sense of fairness, and so on.
But was it really a good idea to diminish the role of Economic Man that much? No, said Friedman, who argued in his 1953 essay “The Methodology of Positive Economics” that economic theories should be judged not by their psychological realism but by their ability to predict behavior. And Friedman’s two greatest triumphs as an economic theorist came from applying the hypothesis of rational behavior to questions other economists had thought beyond its reach.