In his article “Why Philosophical Theories of Evidence Are (and Ought to Be) Ignored by Scientists,” Peter Achinstein argues that philosophical theories of evidence are ignored by scientists because they rest on assumptions which make their concepts of evidence too weak for scientists to work with, or which entail that the truth or falsity of evidential statements can be determined a priori. Given that, as Achinstein argues, the truth of many evidential statements can only be determined empirically, this “a priorist” assumption makes scientists consider philosophical accounts of evidence irrelevant to their work.
In what follows I will examine the value of evidence, its nature, and its relation to science. I hope to show that, while Achinstein’s conclusions are mostly right, the arguments and examples he gives to support them are flawed in some of their details. Specifically, I propose an account of evidence according to which, though evidential claims are objective to a large extent, something counts as evidence only if, ultimately, it has a relation to beings for whom it counts as evidence. On this view something’s status as evidence does not derive merely from people’s beliefs, but from shared practices that are embodied in what I call contexts of inquiry. I also propose that this concept of evidence is one according to which evidential claims, though defeasible, are in one respect a priori. I argue that this account of evidence is one that should be of interest to scientists.