Are Functional Relations Always the Alter Ego of Humean Laws?

It has recently been suggested in the pages of this journal that 'functional relations are the alter ego of Humean laws' (Fleetwood, 2001, p. 205). Based on the identification of an open-systems, ceteris-paribus (OSCP) approach to formal modelling, it is argued that this claim is true only some of the time and problematic only some of the time that it is true. The paper goes on to demonstrate that functional relations that are consistent with the OSCP approach to formal modelling can provide useful tools in various domains of the stratified ontology identified by critical realists. The OSCP approach to formalism is contrasted with a second, axiomatic approach to formalism that is identified as advising the mainstream formal modelling project.