The extraordinary influence of Milton Friedman is largely attributable to the passion and clarity he brought to the defense of competitive markets during the New Deal period when the public entrenchment of monopolies and cartels were standard government policy. Friedman wrote at a time when the field was smaller, specialization was limited, and technical and empirical work relatively undeveloped. Against that background, his lucid prose and emphatic judgments gained him influence that is not likely to be replicated in a more mature and variegated field.