Above all, competition generates useful information and true knowledge. As Justice Oliver Wendell Holmes wrote in a celebrated dissent in the 1919 First Amendment case Abrams v. United States, “the best test of truth is the power of the thought to get itself accepted in the competition of the market.” In economic markets, competition elicits dispersed information about supply, demand, costs, and preferences and transmits it in the form of prices to producers and consumers. In the “marketplace of ideas” — from politics to religion, science to philosophy — competition entails publicizing ideas and testing them against the experiences and observations of others. In some areas, this process produces a consensus of popular or professional opinion. Such consensus invariably changes over time, but in many important fields (such as engineering and the health sciences) it is demonstrably progressive — cumulating and improving rather than oscillating.