To sum up
I have argued that claims about laws, chances, and other modalized structures encode inductions on observed regularities in a form that is tailored to solve the kinds of practical and epistemic problems that beings like us—beings with limited sources of information about the world that gather and store information and use it to guide behavior—face. The account of how we form beliefs about such structures is given by a description of scientific practice, modeled loosely on Lewis’s Best Systems Analysis.
I denied that such beliefs are reducible to beliefs about categorical facts. The reason was that they have modal implications that are crucial to their function and that outrun any claim about what actually happens. I also denied that the extra content does anything more than to project observed regularities into hypothetical situations of the kind that we entertain imaginatively in the course of decision. I characterized the function of these structures on our models generically by saying that they act as PPS’s to FEP’s. Individually, their function is given by a detailed description of the particular role they play in epistemic and practical reasoning. Chances, for example, provide best guesses for creatures confronting an unknown future. Causes highlight strategic routes for bringing about ends. Laws encode general inductive hypotheses that constrain both action and belief. Dispositions and capacities encode other kinds of useful inductions that guide the interaction of the embedded agent with the systems to which they are ascribed. I have not tried to talk anyone out of a metaphysically inflated notion of modality; I have just tried to suggest that there is a sensible story for empiricists to tell about the modal commitments of science that does not saddle them with an objectionable metaphysics. This opens up space for an empiricist account of the central modalized concepts of science that looks at the inductive content they encode, and the role that content plays in our practical and epistemic lives, without trying to reduce or eliminate it.