Laudan, friedman and the role of the a priori in science

This paper critically contrasts Laudan's normative naturalism with Friedman's arguments about the importance of a priori concepts in scientific methodology. I do not take issue with Laudan's claim that taking philosophy and science to be continuous does not preclude a normative role for the philosophy of science. The main focus of criticism instead is Laudan's assertion that if normative philosophy employs the methods found in the sciences themselves, then this precludes any a priori or philosophical justification of methodological rules. I make the case that not only are such justifications possible, they are central to any proper philosophical understanding of scientific methodology, and must figure prominently in any plausible version of normative naturalism. To make this case I sketch Laudan's position and his reasons for the ban on a priori justification. I then contrast Laudan's position with Friedman's recent studies on the prominence of relativised constitutive a priori principles within science and show that this view can serve as the basis of a contrasting variation of naturalised philosophy of science. I elucidate Friedman's position in order to identify some prima facie difficulties with Laudan's ban on the a priori in our understanding of science but also to provide an example of a competing variation of philosophical naturalism. Finally, I further highlight the difficulties that attend Laudan's position through a case study, the central methodological role of renormalisation in quantum field theory.