This paper presents a prescriptive goal-oriented design evaluation model. The approach uses goals or targets as is commonly observed in design practice. After providing motivation for a goal-oriented approach in the early stages of product design the concept and method, based upon subjective probabilities of acceptance, are formalized. A unidimensional acceptability function is defined and the mathematical construction of a multidimensional acceptability function is presented. Issues related to simplicity and measurement accuracy are discussed. Finally, the significance of uncertainty in relation to design improvement potential is discussed. The proposed method is then applied to an engine concept selection problem.