The subject of this chapter is the meaning of the term “persuasion” as a speech act in argumentation theory. Terms like “persuading” and “persuasion” are pervasive and central in recent work in argumentation, along with closely related terms like “convince” and “convincing.” It is often said that the purpose of an argument, for example, is to persuade or convince someone to accept something as true. Wenzel (1990, p. 13) stated that “the purpose of rhetoric is persuasion.” The problem is to define exactly what is meant by the term “persuasion.” For as Wenzel pointed out (p. 13), simply stating that the purpose of rhetoric is persuasion “evokes all the negative connotations associated with both rhetoric and persuasion.” Both are then linked with deception and sophistical trickery. That line of thought was, of course, Plato's view of both rhetoric and the Sophists, as shown in chapter 1. In this chapter it will be shown that persuasion is a legitimate function of argumentation. What does this remark mean? It seems to imply that persuasion is a distinctive type of communicative act in dialogue, a speech act of some sort. From the previous chapters, many clues can be gathered about what persuasion is, within a multi-agent framework. Obviously, it involves some sort of change of opinion or acceptance of a belief, from an initial state to a new state that is the outcome of the act of persuasion.