The focus of this study is Sextus Empiricus's skeptical strategy of how to guard against deceptive arguments in a practical context. Schmitt investigates Sextus's understanding of fallacies and contextualizes it in comparison with those of Aristotle, the Stoics, and Galen. She analyzes Sextus's argument, engaging with the question of which expertise is necessary for the solution of fallacies. Sextus argues against the common view that logic is the relevant expertise, and that instead it is any expertise regarding the objects referred to by the words used in the fallacy. The book shows that Sextus's argument is informed by his empirical background and is in fact a contribution to a medical debate of his time about the relevance of logic for medicine. Furthermore, it argues that Sextus attacks dogmatic doctors of Galen's persuasion.