Reply to Sprenger’s “A Novel Solution to the Problem of Old Evidence”

I discuss a contemporary solution to the Dynamic Problem of Old Evidence (POE), as proposed by Jan Sprenger (2015). Sprenger’s solution combines the Garber–Jeffrey–Niiniluoto (GJN) approach with Howson’s suggestion of counterfactually removing the old evidence from scientists’ belief systems. I argue that in the Dynamic POE, the challenge is to explain how an insight under beliefs in which the old evidence E is known increased the credence of a scientific hypothesis. Therefore, Sprenger’s counterfactual solution, in which E has been artificially removed, does not resolve the problem. I consider several potential responses.