Pre-print, Working paper: This paper proposes a discrete choice duopoly in which products are described and differentiated by their specific attributes. These attributes can be discrete characteristics or differences in continuous variables, such as prices or qualities. Consumers follow a probabilistic reasoning which is consistent with random decision rule models such as Tversky's "Elimination by Aspects" framework (1972a,b). This type of behavior is relevant for small everyday life purchases. The demand system provides a general structure of product differentiation in which special cases are given by classical models of horizontal and vertical differentiation. Existence and uniqueness of a price Nash equilibrium in pure strategies are established in the duopoly. When attributes' utilities vary, comparative statics properties of profits can be explained by "attractiveness" and "differentiation" effects. These effects are combined in a new way compared to the deterministic structures or to the logit duopoly. For example, an increase in the low utility index of attributes strengthens product differentiation.