 Thagard is able to show that such an algorithm effectively echoes a range of familiar observations regarding theory selection. Hypotheses that explain more defeat those that explain less, for example, and simpler hypotheses are to be preferred. In contrast to simple Popperian refutation, ECHO abandons a hypothesis only when a dominating hypothesis is available. Thagard uses the basic approach of explanatory coherence, instantiated in ECHO, in an analysis of a number of historical cases in the history of science, including the abandonment of phlogiston theory in favor of oxygen theory, the Darwinian revolution, and the eventual triumph of Wegener’s plate tectonics and continental drift.