Relatively recent contributions to the policy literature have called into question the utility of the "network" approach to the study of public policy making, including a challenge to long-held views concerning the impact of the structure of policy subsystems on policy change. This article uses empirical evidence accumulated from case studies of four prominent Canadian federal policy sectors over the period 1990-2000 to address this issue. It sets out a model that explains policy change as dependent upon the effects of the articulation of ideas and interests in public policy processes, and generates several hypotheses relating different subsystem configurations to propensities for paradigmatic and intra-paradigmatic policy dynamics. It suggests that the identification of the nature of the policy subsystem in a given policy sector reveals a great deal about its propensity to respond to changes in ideas and interests.