 Kellert’s (1993) focus on chaos models is suggestive of the semantic view of theories, and many texts and articles on chaos focus on models (e.g., logistic map, Henon map, Lorenz attractor). Briefly, on the semantic view, a theory is characterized by (1) some set of models and (2) the hypotheses linking these models with idealized physical systems. The mathematical models discussed in the literature are concrete and fairly well understood, but what about the hypotheses linking chaos models with idealized physical systems? In the chaos literature, there is a great deal of discussion of various robust or universal patterns and the kinds of predictions that can and cannot be made using chaotic models. Moreover, there is a lot of emphasis on qualitative predictions, geometric “mechanisms” and patterns, but this all comes up short of spelling out hypotheses linking chaos models with idealized physical systems. 