The Conscience of a Liberal - Paul Krugman - Books - Review - New York Times: [M]aybe [Paul] Krugman is not really an economist — at least not according to the definition offered more than a century ago by Francis Amasa Walker, the first president of the American Economic Association, who wrote that laissez-faire “was not... the test of economic orthodoxy, merely.... [But] used to decide whether a man were an economist at all.”
I think this approach can be applied to other fields. I should google to find some physicist who, more than a century ago, claimed that accepting Newton's laws of motion was not just orthodoxy but necessary to be considered a physicist at all. The only challenge is that, about a century ago, this was so true that no one felt the need to say it.
Then I would claim that, say the latest Nobel prize winning physicists aren't physicists at all, because they reject f=ma on the grounds that m is not a constant property of an object but depends on the relative velocity of the object and the observer.
downdate: Brad DeLong looked up the actual Walker quote and notes that Walker didn't say what Kennedy claimed he said. Oh well saved me some googling.