Marketers have often attempted to use product classification schemes to provide a "cookery book" for marketing strategy. This so-called commodity school of thought in marketing is argued, in this paper, to be less than fruitful in providing such a cookery book. Porduct classifications are shown to be contingent upon marketing mix elements and assumptions about consumer response. These lead to four specific problems (1) Ex Post Definitions and Circular Logic: Products are classified ex post,and classification theory gives no hint about how to classify new products or to change existing products. (2) The Problem of Induction: Experiences with similar or existing products give few guides to appropriate or optimum strategy. (3) Fuzzy Sets: Product classification of the same product differs according to the nature of the consumer and at different times for the same consumer. (4) Generalizability of Schema: Application of a classification scheme requires the specification of all physical, market and social contexts.