Public policy planning may be in a problematic interregnum partially characterized by an onto-epistemological incongruity between two referent images of reality (Stokes, 1996) where, to paraphrase the Tao Te Ching, "those who know cannot say: those who say do not know. So be it." This response, of course, is seen as wholly unsatisfactory to many.

We are in an interregnum of public policy planning; between approaches characterized by Newtonian models and ideas-that the public policy domain is best modeled as a linear mechanical system-and new approaches drawn from the sciences of complexity. The interregnum corresponds to a period of incomparable deliberation upon the onto- epistemology that has sustained positivistic public policy planning.

Cybernetics, chaos theory, complexity theory and the theory of dissipative structures suggest that the public policy domain is an open nonlinear dynamical system, punctuated by emergent phenomena and characterized by richly integrated yet often-ambiguous, feedback relationships. Sustained by the onto-epistemological convention, the continued use of conventional models, though not without occasional successes, will serve to increase the risk and failure rate of public policy initiatives, which in a Panglossian manner, will encourage a greater demand for the ever more rigorous application of conventional thinking, leading to another round of failure. The emerging insights from the sciences of complexity need to be complemented by a major methodological initiative. This is needed to formalize new models and operationalize public policy planning in pursuit of constructive social change.