Nonlinear Thermodynamics and Social Science Modeling: Fad Cycles, Cultural Development and Identijicational Slips By ELIAS L. KHALIL ABSTRACT. The paper argues that the application of nonlinear dynamics bor- rowed from thermodynamics for the study of the evolution of institutions amounts to an identificational slip. While the paper welcomes the importation of techniques from the natural sciences, thermodynamic feedback is simply an inappropriate technique for the study of evolutionary change. Thermodynamic feedback is only appropriate for the study of social dynamicsUke mob behavior, stock war/fee/gyrations, zndfadcydes. One should rather appeal to the evolution of species—as recorded by change of gene frequency and phenotypic traits— as the appropriate metaphor for the study of evolution of culture—as manifested by change of rules and principles and their consequent order. I Introduction MANY SOCIAL SCIENTISTS AND HISTORIANS appear to confuse two kinds of historical change when they study socio-political phenomena.' With the advent of non- linear dynamics metaphors, chaos theory, Prigogine's dissipative structures, spin glass models, Haken's synergetics, Thom's catastrophe theory, and so on, some historians have tended to apply such tools, which are appropriate to dynamics, to the study of developmental processes as well. But the nonlinear phenomena in physics would be at best homologous to only one kind of temporal change, viz., dynamics. Stated straightforwardly, modeling developmental processes of cultural evo- lution and deep socio-political change after Ilya Prigogine's, (e.g., 1980), notion "dissipative structure," Hermann Haken's {\911, in Khalil & Boulding, 1996) idea "hierarchy of order parameters," Rene Thom's (1975) catastrophe discon- tinuity, or any other fashionable theory of dynamics would amount to an iden- tificational slip (Khalil, 1993b). Prigogine's research on far-from-equilibrium • [Elias L. Khalil, PhD., is assistant professor of economics at Ohio State Univerity, 1680 University Drive, Mansfield, OH 44906, and the Institute for Study of Economic Evolution, University of Freiburg, Freiburg D-79085, Germany.) The comments of Victor Burke, Randolph Roth, Philip Pomper, Barkley Rosser and anonymous referees are appreciated and the technical help of Carole Brown and Beth Burns acknowledged. American Journal of Economics and Sociology, Vol. 54, No. 4 (Oclober, 1995). © 1995 American Journal of Economics and Sociology, Inc.