This monograph presents a general equilibrium methodology for microeconomic policy analysis intended to serve as an alternative to the now classical, axiomatic general equilibrium theory as exposited in Debreu's Theory of Value(1959) or Arrow and Hahn's General Competitive Analysis(1971).The methodology proposed in this monograph does not presume the existence of market equilibrium,accepts the inherent indeterminancy of nonparametric general equlibrium models,and offers effective algorithms for computing counterfactual equilibria in these models.It consists of several essays written over the last decade,some with colleagues or former graduate students,and an appendix by Charles Steinhorn on the elements of O-minimal structures,the mathematical framework for our analysis