Abstract

The expression of a physical law has usually been understood as a description. Among the entities that different philosophers have maintained that nomic expressions describe are regularities among events or states of affairs, natural necessities, and relations among universals. I maintain that nomic expressions are better understood not as serving a descriptive function but as in many respects playing a prescriptive role; the expression of a physical law, I argue, says that one ought to regard certain claims as able to justify certain other claims. On the basis of this proposal, I advance a response to Hempel's "problem of provisos" and a conception of inductive inference as the reasoned adoption of claims prescribing that certain inferences be considered good. I argue that on this account of laws, the contraposition of a nomic expression need not express a law; by properly distinguishing the confirmation of a claim's nomologicality from the confirmation of a claim's truth, this account of inductive inference can avoid Hempel's raven paradox. I hold that this approach to confirmation leads to a novel conception of the relation between empirical and non-empirical criteria of theory-choice, as well as to proposals concerning the grue problem and the role of theoretical terms in the confirmation of a claim's nomologicality. I further argue that in order to offer any reasons at all for treating persons as qualified to make a certain kind of observation-report in virtue of their behavior under certain circumstances, one must be prepared to adopt nomic expressions that endorse what Hume considered to be risky inferences. I contend that this result constitutes a promising basis for accounts of scientific progress and of the rationality of inductive inference. By deliberating about which expressions to adopt as nomic, i.e., by reasoning about what claims we ought to count as good reasons for what other claims, we can get an argumentative grip on our justificatory practices; as a progressively greater portion of our language-use comes into accord with the prescriptions that we have adopted as nomic expressions, the proprieties that govern our language-use become increasingly of our own design