Experimental individuation and philosophical retail arguments

This paper aims to defend the use of the notion of experimental individuation, which has recently been developed by Ruey-Lin Chen, as a criterion for the reality of theoretical entities. In short, when scientists experimentally individuate an entity, a realist conclusion about that entity is warranted. We embed this claim regarding experimental individuation within a framework that allows for other criteria of reality. And we understand so-called retail arguments regarding the reality of a particular theoretical entity as arguments that concern choosing an appropriate criterion of reality for that entity and determining whether the relevant first-order scientific evidence satisfies that criterion. We argue that such retail arguments are philosophical because defending criteria of reality, and showing that they are or are not satisfied in particular cases, involves work that is distinctively philosophical. And we illustrate this philosophical work by applying our criterion of experimental individuation to three historical cases: Davy’s potassium, Lavoisier’s muriatic radical, and Thomson’s electrified particles.