To develop an empiricist account of science is to depict it as involving a search for truth only about the empirical world, aboutwhat is actual and observable.... It must involve throughout a resolute rejection of the demand for an explanation of the regularities in the observable course of nature, by means of truths concerning a reality beyond what is actual and observable, as a demand which plays no role in the scientific enterprise.
Philosophers often think all scientists must be scientific realists. If you ask a simple question like "Are electrons real?" the answer will be "Yes". But if your questions are less superficial, for example whether some well-known scientist was a good scientist. Then, they had insisted that only empirical criteria matter and that they actually did not believe in the reality of sub-atomic entities. Ask "If that turned out to be true, would you still say they were good scientists?" The answer would reveal something about how they themselves understood what it is to be a scientist.
Certain issues in philosophy of science (having to do with observation and the definition of a theory's empirical import) had beenmisconstrued as issues in philosophy of logic and of language. With respect to modality, I hold the exact opposite: important philosophical problems concerning language have been misconstrued as relating to the content of science and the nature of the world. This is not at all new, but is the traditional nominalist line.