I. Introduction: Managerialism, behavioralism, and the competitive model, 237. — II. Firm decision processes and the “as if” argument, 240. — III. Selection, decision rules, and competitive outcomes, 244. — IV. A competitive industry: Orthodox analysis, 248. — V. A competitive industry: Assumptions of the selection model, 249. — VI. Proof of the theorem, 254. — VII. Extensions and generalizations, 257. — VIII. Schumpeterian competition, 259. — IX. Concluding comments, 260. — Appendix: Proof of the existence of competitive equilibrium, 261.