‘When the facts change, I change my mind. What do you do, sir?”
There are competing accounts of the authorship of this affirmation of the importance of empiricism to the intellectual method. It used to be claimed for John Maynard Keynes. As with almost every quotable observation of the last 150 years it has been attributed to Winston Churchill. Most people now think it was more likely the work of Paul Samuelson.
Whoever said it first, it seems almost quaintly nostalgic in our age of individual epistemic autonomy, when facts are infinitely fungible and take second place to our ideological priors. An updated version of the adage might be: When the facts change, I deny them, ascribe them to some malevolent opponent, and then imagine another set of facts that allow me to leave my mind unchanged. What do you do, sir?
We’ve seen plenty of this epistemic nimbleness in the last year, with scientific claims that large gatherings threaten public health except when they’re in service of racial justice, or that political violence threatens public order only when it comes from the right.
As Samuelson could attest, economics is more prone to the temptations of fact-selectivity than any other discipline, and our current macroeconomic policy debate is no exception.