Four philosophers comment on foundations and substance of applied economics. Pitt focuses on rational decision making and stresses the importance of choice although he faults the economics model as a predictor of behavior. Buchanan argues that comparisons of whole economic systems on the basis of efficiency are doubtful if not impossible. MacLean and Mills examine the hazards of confusing normative and empirical statements about behavior. All papers provide constructive comments on the model making and testing processes of applied economics.