Legal Philosophy

Via the Volokh Conspiracy, here's an article about "legal formalism" vs. "realism" or maybe "instrumentalism." I have little (ok, no) understanding of this sort of thing. Surely there are no "formalists" who really believe that all cases are determined, and no "realists" who believe that none are (and that everything should be decided as a matter of policy). Is it just a matter of who thinks what's more important in deciding hard cases? How much attention do judges and justices pay to this sort of debate?