Chapter 16 summarizes the argument and shows that the methodological peculiarities of economics depend to a considerable extent on the fact that it is a social science. The fact that equilibrium theory includes a theory of rationality helps to explain why positive and normative economics are so intermingled, why economists are so strongly committed to their theory, and why they pursue a distinctive strategy.

Chapter 9 develops the traditional conception of economics as an inexact science that investigates deductively the implications of assumptions that are known to be true statements of tendencies, but that are only approximately true as generalizations concerning behavior. I consider interpretations of the problematic notion of inexactness as probabilistic, as approximate, as qualified with ceteris paribus clauses, and as stating tendencies that state the contribution that causes make to outcomes and hence how things would be in the absence of interferences. The chapter argues for an account that combines a view of inexactness in terms of tendencies with an account in terms of implicit qualification. Chapter 9 explains how statements of tendencies can be true.